CINXE.COM

<!DOCTYPE html> <html class="client-nojs vector-feature-language-in-header-enabled vector-feature-language-in-main-page-header-disabled vector-feature-page-tools-pinned-disabled vector-feature-toc-pinned-clientpref-1 vector-feature-main-menu-pinned-disabled vector-feature-limited-width-clientpref-1 vector-feature-limited-width-content-enabled vector-feature-custom-font-size-clientpref-1 vector-feature-appearance-pinned-clientpref-1 vector-feature-night-mode-enabled skin-theme-clientpref-day vector-sticky-header-enabled vector-toc-available" lang="en" dir="ltr"> <head> <meta charset="UTF-8"> <title>Focal length - Wikipedia</title> <script>(function(){var className="client-js vector-feature-language-in-header-enabled vector-feature-language-in-main-page-header-disabled vector-feature-page-tools-pinned-disabled vector-feature-toc-pinned-clientpref-1 vector-feature-main-menu-pinned-disabled vector-feature-limited-width-clientpref-1 vector-feature-limited-width-content-enabled vector-feature-custom-font-size-clientpref-1 vector-feature-appearance-pinned-clientpref-1 vector-feature-night-mode-enabled skin-theme-clientpref-day vector-sticky-header-enabled vector-toc-available";var cookie=document.cookie.match(/(?:^|; )enwikimwclientpreferences=([^;]+)/);if(cookie){cookie[1].split('%2C').forEach(function(pref){className=className.replace(new RegExp('(^| )'+pref.replace(/-clientpref-\w+$|[^\w-]+/g,'')+'-clientpref-\\w+( |$)'),'$1'+pref+'$2');});}document.documentElement.className=className;}());RLCONF={"wgBreakFrames":false,"wgSeparatorTransformTable":["",""],"wgDigitTransformTable":["",""],"wgDefaultDateFormat":"dmy","wgMonthNames":["","January","February","March","April","May","June","July","August","September","October","November","December"],"wgRequestId":"d3bc8056-6feb-49fc-8b93-ae9c2dd56f2e","wgCanonicalNamespace":"","wgCanonicalSpecialPageName":false,"wgNamespaceNumber":0,"wgPageName":"Focal_length","wgTitle":"Focal length","wgCurRevisionId":1280478286,"wgRevisionId":1280478286,"wgArticleId":82269,"wgIsArticle":true,"wgIsRedirect":false,"wgAction":"view","wgUserName":null,"wgUserGroups":["*"],"wgCategories":["Articles with short description","Short description matches Wikidata","Articles needing additional references from November 2021","All articles needing additional references","Commons category link is on Wikidata","Geometrical optics","Length","Science of photography","Optical quantities"],"wgPageViewLanguage":"en","wgPageContentLanguage":"en","wgPageContentModel":"wikitext","wgRelevantPageName":"Focal_length","wgRelevantArticleId":82269,"wgIsProbablyEditable":true,"wgRelevantPageIsProbablyEditable":true,"wgRestrictionEdit":[],"wgRestrictionMove":[],"wgNoticeProject":"wikipedia","wgCiteReferencePreviewsActive":false,"wgFlaggedRevsParams":{"tags":{"status":{"levels":1}}},"wgMediaViewerOnClick":true,"wgMediaViewerEnabledByDefault":true,"wgPopupsFlags":0,"wgVisualEditor":{"pageLanguageCode":"en","pageLanguageDir":"ltr","pageVariantFallbacks":"en"},"wgMFDisplayWikibaseDescriptions":{"search":true,"watchlist":true,"tagline":false,"nearby":true},"wgWMESchemaEditAttemptStepOversample":false,"wgWMEPageLength":20000,"wgEditSubmitButtonLabelPublish":true,"wgULSPosition":"interlanguage","wgULSisCompactLinksEnabled":false,"wgVector2022LanguageInHeader":true,"wgULSisLanguageSelectorEmpty":false,"wgWikibaseItemId":"Q193540","wgCheckUserClientHintsHeadersJsApi":["brands","architecture","bitness","fullVersionList","mobile","model","platform","platformVersion"],"GEHomepageSuggestedEditsEnableTopics":true,"wgGETopicsMatchModeEnabled":false,"wgGELevelingUpEnabledForUser":false}; RLSTATE={"ext.globalCssJs.user.styles":"ready","site.styles":"ready","user.styles":"ready","ext.globalCssJs.user":"ready","user":"ready","user.options":"loading","ext.math.styles":"ready","ext.cite.styles":"ready","skins.vector.search.codex.styles":"ready","skins.vector.styles":"ready","skins.vector.icons":"ready","jquery.makeCollapsible.styles":"ready","ext.wikimediamessages.styles":"ready","ext.visualEditor.desktopArticleTarget.noscript":"ready","ext.uls.interlanguage":"ready","wikibase.client.init":"ready"};RLPAGEMODULES=["ext.cite.ux-enhancements","mediawiki.page.media","site","mediawiki.page.ready","jquery.makeCollapsible","mediawiki.toc","skins.vector.js","ext.centralNotice.geoIP","ext.centralNotice.startUp","ext.gadget.ReferenceTooltips","ext.gadget.switcher","ext.urlShortener.toolbar","ext.centralauth.centralautologin","mmv.bootstrap","ext.popups","ext.visualEditor.desktopArticleTarget.init","ext.visualEditor.targetLoader","ext.echo.centralauth","ext.eventLogging","ext.wikimediaEvents","ext.navigationTiming","ext.uls.interface","ext.cx.eventlogging.campaigns","ext.cx.uls.quick.actions","wikibase.client.vector-2022","ext.checkUser.clientHints","ext.quicksurveys.init","ext.growthExperiments.SuggestedEditSession"];</script> <script>(RLQ=window.RLQ||[]).push(function(){mw.loader.impl(function(){return["user.options@12s5i",function($,jQuery,require,module){mw.user.tokens.set({"patrolToken":"+\\","watchToken":"+\\","csrfToken":"+\\"}); }];});});</script> <link rel="stylesheet" href="/w/load.php?lang=en&modules=ext.cite.styles%7Cext.math.styles%7Cext.uls.interlanguage%7Cext.visualEditor.desktopArticleTarget.noscript%7Cext.wikimediamessages.styles%7Cjquery.makeCollapsible.styles%7Cskins.vector.icons%2Cstyles%7Cskins.vector.search.codex.styles%7Cwikibase.client.init&only=styles&skin=vector-2022"> <script async="" src="/w/load.php?lang=en&modules=startup&only=scripts&raw=1&skin=vector-2022"></script> <meta name="ResourceLoaderDynamicStyles" content=""> <link rel="stylesheet" href="/w/load.php?lang=en&modules=site.styles&only=styles&skin=vector-2022"> <meta name="generator" content="MediaWiki 1.44.0-wmf.21"> <meta name="referrer" content="origin"> <meta name="referrer" content="origin-when-cross-origin"> <meta name="robots" content="max-image-preview:standard"> <meta name="format-detection" content="telephone=no"> <meta name="viewport" content="width=1120"> <meta property="og:title" content="Focal length - Wikipedia"> <meta property="og:type" content="website"> <link rel="preconnect" href="//upload.wikimedia.org"> <link rel="alternate" media="only screen and (max-width: 640px)" href="//en.m.wikipedia.org/wiki/Focal_length"> <link rel="alternate" type="application/x-wiki" title="Edit this page" href="/w/index.php?title=Focal_length&action=edit"> <link rel="apple-touch-icon" href="/static/apple-touch/wikipedia.png"> <link rel="icon" href="/static/favicon/wikipedia.ico"> <link rel="search" type="application/opensearchdescription+xml" href="/w/rest.php/v1/search" title="Wikipedia (en)"> <link rel="EditURI" type="application/rsd+xml" href="//en.wikipedia.org/w/api.php?action=rsd"> <link rel="canonical" href="https://en.wikipedia.org/wiki/Focal_length"> <link rel="license" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en"> <link rel="alternate" type="application/atom+xml" title="Wikipedia Atom feed" href="/w/index.php?title=Special:RecentChanges&feed=atom"> <link rel="dns-prefetch" href="//meta.wikimedia.org" /> <link rel="dns-prefetch" href="login.wikimedia.org"> </head> <body class="skin--responsive skin-vector skin-vector-search-vue mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject mw-editable page-Focal_length rootpage-Focal_length skin-vector-2022 action-view"><a class="mw-jump-link" href="#bodyContent">Jump to content</a> <div class="vector-header-container"> <header class="vector-header mw-header"> <div class="vector-header-start"> <nav class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-dropdown" class="vector-dropdown vector-main-menu-dropdown vector-button-flush-left vector-button-flush-right" title="Main menu" > <input type="checkbox" id="vector-main-menu-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-main-menu-dropdown" class="vector-dropdown-checkbox " aria-label="Main menu" > <label id="vector-main-menu-dropdown-label" for="vector-main-menu-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-menu mw-ui-icon-wikimedia-menu"></span> <span class="vector-dropdown-label-text">Main menu</span> </label> <div class="vector-dropdown-content"> <div id="vector-main-menu-unpinned-container" class="vector-unpinned-container"> <div id="vector-main-menu" class="vector-main-menu vector-pinnable-element"> <div class="vector-pinnable-header vector-main-menu-pinnable-header vector-pinnable-header-unpinned" data-feature-name="main-menu-pinned" data-pinnable-element-id="vector-main-menu" data-pinned-container-id="vector-main-menu-pinned-container" data-unpinned-container-id="vector-main-menu-unpinned-container" > <div class="vector-pinnable-header-label">Main menu</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-main-menu.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-main-menu.unpin">hide</button> </div> <div id="p-navigation" class="vector-menu mw-portlet mw-portlet-navigation" > <div class="vector-menu-heading"> Navigation </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="n-mainpage-description" class="mw-list-item"><a href="/wiki/Main_Page" title="Visit the main page [z]" accesskey="z"><span>Main page</span></a></li><li id="n-contents" class="mw-list-item"><a href="/wiki/Wikipedia:Contents" title="Guides to browsing Wikipedia"><span>Contents</span></a></li><li id="n-currentevents" class="mw-list-item"><a href="/wiki/Portal:Current_events" title="Articles related to current events"><span>Current events</span></a></li><li id="n-randompage" class="mw-list-item"><a href="/wiki/Special:Random" title="Visit a randomly selected article [x]" accesskey="x"><span>Random article</span></a></li><li id="n-aboutsite" class="mw-list-item"><a href="/wiki/Wikipedia:About" title="Learn about Wikipedia and how it works"><span>About Wikipedia</span></a></li><li id="n-contactpage" class="mw-list-item"><a href="//en.wikipedia.org/wiki/Wikipedia:Contact_us" title="How to contact Wikipedia"><span>Contact us</span></a></li> </ul> </div> </div> <div id="p-interaction" class="vector-menu mw-portlet mw-portlet-interaction" > <div class="vector-menu-heading"> Contribute </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="n-help" class="mw-list-item"><a href="/wiki/Help:Contents" title="Guidance on how to use and edit Wikipedia"><span>Help</span></a></li><li id="n-introduction" class="mw-list-item"><a href="/wiki/Help:Introduction" title="Learn how to edit Wikipedia"><span>Learn to edit</span></a></li><li id="n-portal" class="mw-list-item"><a href="/wiki/Wikipedia:Community_portal" title="The hub for editors"><span>Community portal</span></a></li><li id="n-recentchanges" class="mw-list-item"><a href="/wiki/Special:RecentChanges" title="A list of recent changes to Wikipedia [r]" accesskey="r"><span>Recent changes</span></a></li><li id="n-upload" class="mw-list-item"><a href="/wiki/Wikipedia:File_upload_wizard" title="Add images or other media for use on Wikipedia"><span>Upload file</span></a></li><li id="n-specialpages" class="mw-list-item"><a href="/wiki/Special:SpecialPages"><span>Special pages</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> <a href="/wiki/Main_Page" class="mw-logo"> <img class="mw-logo-icon" src="/static/images/icons/wikipedia.png" alt="" aria-hidden="true" height="50" width="50"> <span class="mw-logo-container skin-invert"> <img class="mw-logo-wordmark" alt="Wikipedia" src="/static/images/mobile/copyright/wikipedia-wordmark-en.svg" style="width: 7.5em; height: 1.125em;"> <img class="mw-logo-tagline" alt="The Free Encyclopedia" src="/static/images/mobile/copyright/wikipedia-tagline-en.svg" width="117" height="13" style="width: 7.3125em; height: 0.8125em;"> </span> </a> </div> <div class="vector-header-end"> <div id="p-search" role="search" class="vector-search-box-vue vector-search-box-collapses vector-search-box-show-thumbnail vector-search-box-auto-expand-width vector-search-box"> <a href="/wiki/Special:Search" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only search-toggle" title="Search Wikipedia [f]" accesskey="f"><span class="vector-icon mw-ui-icon-search mw-ui-icon-wikimedia-search"></span> <span>Search</span> </a> <div class="vector-typeahead-search-container"> <div class="cdx-typeahead-search cdx-typeahead-search--show-thumbnail cdx-typeahead-search--auto-expand-width"> <form action="/w/index.php" id="searchform" class="cdx-search-input cdx-search-input--has-end-button"> <div id="simpleSearch" class="cdx-search-input__input-wrapper" data-search-loc="header-moved"> <div class="cdx-text-input cdx-text-input--has-start-icon"> <input class="cdx-text-input__input" type="search" name="search" placeholder="Search Wikipedia" aria-label="Search Wikipedia" autocapitalize="sentences" title="Search Wikipedia [f]" accesskey="f" id="searchInput" > <span class="cdx-text-input__icon cdx-text-input__start-icon"></span> </div> <input type="hidden" name="title" value="Special:Search"> </div> <button class="cdx-button cdx-search-input__end-button">Search</button> </form> </div> </div> </div> <nav class="vector-user-links vector-user-links-wide" aria-label="Personal tools"> <div class="vector-user-links-main"> <div id="p-vector-user-menu-preferences" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <div id="p-vector-user-menu-userpage" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-dropdown" class="vector-dropdown " title="Change the appearance of the page's font size, width, and color" > <input type="checkbox" id="vector-appearance-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-appearance-dropdown" class="vector-dropdown-checkbox " aria-label="Appearance" > <label id="vector-appearance-dropdown-label" for="vector-appearance-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-appearance mw-ui-icon-wikimedia-appearance"></span> <span class="vector-dropdown-label-text">Appearance</span> </label> <div class="vector-dropdown-content"> <div id="vector-appearance-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <div id="p-vector-user-menu-notifications" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <div id="p-vector-user-menu-overflow" class="vector-menu mw-portlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="https://donate.wikimedia.org/?wmf_source=donate&wmf_medium=sidebar&wmf_campaign=en.wikipedia.org&uselang=en" class=""><span>Donate</span></a> </li> <li id="pt-createaccount-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:CreateAccount&returnto=Focal+length" title="You are encouraged to create an account and log in; however, it is not mandatory" class=""><span>Create account</span></a> </li> <li id="pt-login-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:UserLogin&returnto=Focal+length" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o" class=""><span>Log in</span></a> </li> </ul> </div> </div> </div> <div id="vector-user-links-dropdown" class="vector-dropdown vector-user-menu vector-button-flush-right vector-user-menu-logged-out" title="Log in and more options" > <input type="checkbox" id="vector-user-links-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-user-links-dropdown" class="vector-dropdown-checkbox " aria-label="Personal tools" > <label id="vector-user-links-dropdown-label" for="vector-user-links-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-ellipsis mw-ui-icon-wikimedia-ellipsis"></span> <span class="vector-dropdown-label-text">Personal tools</span> </label> <div class="vector-dropdown-content"> <div id="p-personal" class="vector-menu mw-portlet mw-portlet-personal user-links-collapsible-item" title="User menu" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport" class="user-links-collapsible-item mw-list-item"><a href="https://donate.wikimedia.org/?wmf_source=donate&wmf_medium=sidebar&wmf_campaign=en.wikipedia.org&uselang=en"><span>Donate</span></a></li><li id="pt-createaccount" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:CreateAccount&returnto=Focal+length" title="You are encouraged to create an account and log in; however, it is not mandatory"><span class="vector-icon mw-ui-icon-userAdd mw-ui-icon-wikimedia-userAdd"></span> <span>Create account</span></a></li><li id="pt-login" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:UserLogin&returnto=Focal+length" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o"><span class="vector-icon mw-ui-icon-logIn mw-ui-icon-wikimedia-logIn"></span> <span>Log in</span></a></li> </ul> </div> </div> <div id="p-user-menu-anon-editor" class="vector-menu mw-portlet mw-portlet-user-menu-anon-editor" > <div class="vector-menu-heading"> Pages for logged out editors <a href="/wiki/Help:Introduction" aria-label="Learn more about editing"><span>learn more</span></a> </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-anoncontribs" class="mw-list-item"><a href="/wiki/Special:MyContributions" title="A list of edits made from this IP address [y]" accesskey="y"><span>Contributions</span></a></li><li id="pt-anontalk" class="mw-list-item"><a href="/wiki/Special:MyTalk" title="Discussion about edits from this IP address [n]" accesskey="n"><span>Talk</span></a></li> </ul> </div> </div> </div> </div> </nav> </div> </header> </div> <div class="mw-page-container"> <div class="mw-page-container-inner"> <div class="vector-sitenotice-container"> <div id="siteNotice"></div> </div> <div class="vector-column-start"> <div class="vector-main-menu-container"> <div id="mw-navigation"> <nav id="mw-panel" class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-pinned-container" class="vector-pinned-container"> </div> </nav> </div> </div> <div class="vector-sticky-pinned-container"> <nav id="mw-panel-toc" aria-label="Contents" data-event-name="ui.sidebar-toc" class="mw-table-of-contents-container vector-toc-landmark"> <div id="vector-toc-pinned-container" class="vector-pinned-container"> <div id="vector-toc" class="vector-toc vector-pinnable-element"> <div class="vector-pinnable-header vector-toc-pinnable-header vector-pinnable-header-pinned" data-feature-name="toc-pinned" data-pinnable-element-id="vector-toc" > <h2 class="vector-pinnable-header-label">Contents</h2> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-toc.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-toc.unpin">hide</button> </div> <ul class="vector-toc-contents" id="mw-panel-toc-list"> <li id="toc-mw-content-text" class="vector-toc-list-item vector-toc-level-1"> <a href="#" class="vector-toc-link"> <div class="vector-toc-text">(Top)</div> </a> </li> <li id="toc-Thin_lens_approximation" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Thin_lens_approximation"> <div class="vector-toc-text"> <span class="vector-toc-numb">1</span> <span>Thin lens approximation</span> </div> </a> <ul id="toc-Thin_lens_approximation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-General_optical_systems" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#General_optical_systems"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>General optical systems</span> </div> </a> <ul id="toc-General_optical_systems-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-In_photography" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#In_photography"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>In photography</span> </div> </a> <ul id="toc-In_photography-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Optical_power" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Optical_power"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Optical power</span> </div> </a> <ul id="toc-Optical_power-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Table of Contents" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Focal length</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 55 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-55" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">55 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-af mw-list-item"><a href="https://af.wikipedia.org/wiki/Fokusafstand" title="Fokusafstand – Afrikaans" lang="af" hreflang="af" data-title="Fokusafstand" data-language-autonym="Afrikaans" data-language-local-name="Afrikaans" class="interlanguage-link-target"><span>Afrikaans</span></a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D8%A8%D8%B9%D8%AF_%D8%A8%D8%A4%D8%B1%D9%8A" title="بعد بؤري – Arabic" lang="ar" hreflang="ar" data-title="بعد بؤري" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-ast mw-list-item"><a href="https://ast.wikipedia.org/wiki/Distancia_focal" title="Distancia focal – Asturian" lang="ast" hreflang="ast" data-title="Distancia focal" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%AB%E0%A7%8B%E0%A6%95%E0%A6%BE%E0%A6%B8_%E0%A6%A6%E0%A7%82%E0%A6%B0%E0%A6%A4%E0%A7%8D%E0%A6%AC" title="ফোকাস দূরত্ব – Bangla" lang="bn" hreflang="bn" data-title="ফোকাস দূরত্ব" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%A4%D0%BE%D0%BA%D1%83%D1%81%D0%BD%D0%B0%D1%8F_%D0%B0%D0%B4%D0%BB%D0%B5%D0%B3%D0%BB%D0%B0%D1%81%D1%86%D1%8C" title="Фокусная адлегласць – Belarusian" lang="be" hreflang="be" data-title="Фокусная адлегласць" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%A4%D0%BE%D0%BA%D1%83%D1%81%D0%BD%D0%BE_%D1%80%D0%B0%D0%B7%D1%81%D1%82%D0%BE%D1%8F%D0%BD%D0%B8%D0%B5" title="Фокусно разстояние – Bulgarian" lang="bg" hreflang="bg" data-title="Фокусно разстояние" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-bar mw-list-item"><a href="https://bar.wikipedia.org/wiki/Brennweidn" title="Brennweidn – Bavarian" lang="bar" hreflang="bar" data-title="Brennweidn" data-language-autonym="Boarisch" data-language-local-name="Bavarian" class="interlanguage-link-target"><span>Boarisch</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Dist%C3%A0ncia_focal" title="Distància focal – Catalan" lang="ca" hreflang="ca" data-title="Distància focal" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Ohniskov%C3%A1_vzd%C3%A1lenost" title="Ohnisková vzdálenost – Czech" lang="cs" hreflang="cs" data-title="Ohnisková vzdálenost" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Br%C3%A6ndvidde" title="Brændvidde – Danish" lang="da" hreflang="da" data-title="Brændvidde" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Brennweite" title="Brennweite – German" lang="de" hreflang="de" data-title="Brennweite" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Fookuskaugus" title="Fookuskaugus – Estonian" lang="et" hreflang="et" data-title="Fookuskaugus" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/%CE%95%CF%83%CF%84%CE%B9%CE%B1%CE%BA%CE%AE_%CE%B1%CF%80%CF%8C%CF%83%CF%84%CE%B1%CF%83%CE%B7" title="Εστιακή απόσταση – Greek" lang="el" hreflang="el" data-title="Εστιακή απόσταση" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Distancia_focal" title="Distancia focal – Spanish" lang="es" hreflang="es" data-title="Distancia focal" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/%C4%88efa_fokusa_distanco" title="Ĉefa fokusa distanco – Esperanto" lang="eo" hreflang="eo" data-title="Ĉefa fokusa distanco" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Foku-distantzia" title="Foku-distantzia – Basque" lang="eu" hreflang="eu" data-title="Foku-distantzia" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D9%81%D8%A7%D8%B5%D9%84%D9%87_%DA%A9%D8%A7%D9%86%D9%88%D9%86%DB%8C_%D8%B9%D8%AF%D8%B3%DB%8C" title="فاصله کانونی عدسی – Persian" lang="fa" hreflang="fa" data-title="فاصله کانونی عدسی" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Focale" title="Focale – French" lang="fr" hreflang="fr" data-title="Focale" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EC%B4%88%EC%A0%90%EA%B1%B0%EB%A6%AC" title="초점거리 – Korean" lang="ko" hreflang="ko" data-title="초점거리" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%AB%E0%A5%8B%E0%A4%95%E0%A4%B8_%E0%A4%A6%E0%A5%82%E0%A4%B0%E0%A5%80" title="फोकस दूरी – Hindi" lang="hi" hreflang="hi" data-title="फोकस दूरी" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/%C5%BDari%C5%A1na_duljina" title="Žarišna duljina – Croatian" lang="hr" hreflang="hr" data-title="Žarišna duljina" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Jarak_fokus" title="Jarak fokus – Indonesian" lang="id" hreflang="id" data-title="Jarak fokus" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-ia mw-list-item"><a href="https://ia.wikipedia.org/wiki/Distantia_focal" title="Distantia focal – Interlingua" lang="ia" hreflang="ia" data-title="Distantia focal" data-language-autonym="Interlingua" data-language-local-name="Interlingua" class="interlanguage-link-target"><span>Interlingua</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Lunghezza_focale" title="Lunghezza focale – Italian" lang="it" hreflang="it" data-title="Lunghezza focale" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-ht mw-list-item"><a href="https://ht.wikipedia.org/wiki/Distans_fokal" title="Distans fokal – Haitian Creole" lang="ht" hreflang="ht" data-title="Distans fokal" data-language-autonym="Kreyòl ayisyen" data-language-local-name="Haitian Creole" class="interlanguage-link-target"><span>Kreyòl ayisyen</span></a></li><li class="interlanguage-link interwiki-lb mw-list-item"><a href="https://lb.wikipedia.org/wiki/Brennw%C3%A4it" title="Brennwäit – Luxembourgish" lang="lb" hreflang="lb" data-title="Brennwäit" data-language-autonym="Lëtzebuergesch" data-language-local-name="Luxembourgish" class="interlanguage-link-target"><span>Lëtzebuergesch</span></a></li><li class="interlanguage-link interwiki-lt mw-list-item"><a href="https://lt.wikipedia.org/wiki/%C5%BDidinio_nuotolis" title="Židinio nuotolis – Lithuanian" lang="lt" hreflang="lt" data-title="Židinio nuotolis" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/F%C3%B3kuszt%C3%A1vols%C3%A1g" title="Fókusztávolság – Hungarian" lang="hu" hreflang="hu" data-title="Fókusztávolság" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target"><span>Magyar</span></a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%AB%E0%B5%8B%E0%B4%95%E0%B5%8D%E0%B4%95%E0%B4%B8%E0%B5%8D_%E0%B4%A6%E0%B5%82%E0%B4%B0%E0%B4%82" title="ഫോക്കസ് ദൂരം – Malayalam" lang="ml" hreflang="ml" data-title="ഫോക്കസ് ദൂരം" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Jarak_fokus" title="Jarak fokus – Malay" lang="ms" hreflang="ms" data-title="Jarak fokus" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Brandpuntsafstand" title="Brandpuntsafstand – Dutch" lang="nl" hreflang="nl" data-title="Brandpuntsafstand" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E7%84%A6%E7%82%B9%E8%B7%9D%E9%9B%A2" title="焦点距離 – Japanese" lang="ja" hreflang="ja" data-title="焦点距離" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Brennvidde" title="Brennvidde – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Brennvidde" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Brennvidd" title="Brennvidd – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Brennvidd" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-oc mw-list-item"><a href="https://oc.wikipedia.org/wiki/Focala" title="Focala – Occitan" lang="oc" hreflang="oc" data-title="Focala" data-language-autonym="Occitan" data-language-local-name="Occitan" class="interlanguage-link-target"><span>Occitan</span></a></li><li class="interlanguage-link interwiki-uz mw-list-item"><a href="https://uz.wikipedia.org/wiki/Fokus_masofasi" title="Fokus masofasi – Uzbek" lang="uz" hreflang="uz" data-title="Fokus masofasi" data-language-autonym="Oʻzbekcha / ўзбекча" data-language-local-name="Uzbek" class="interlanguage-link-target"><span>Oʻzbekcha / ўзбекча</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Ogniskowa" title="Ogniskowa – Polish" lang="pl" hreflang="pl" data-title="Ogniskowa" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Dist%C3%A2ncia_focal" title="Distância focal – Portuguese" lang="pt" hreflang="pt" data-title="Distância focal" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/Distan%C8%9B%C4%83_focal%C4%83" title="Distanță focală – Romanian" lang="ro" hreflang="ro" data-title="Distanță focală" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%A4%D0%BE%D0%BA%D1%83%D1%81%D0%BD%D0%BE%D0%B5_%D1%80%D0%B0%D1%81%D1%81%D1%82%D0%BE%D1%8F%D0%BD%D0%B8%D0%B5" title="Фокусное расстояние – Russian" lang="ru" hreflang="ru" data-title="Фокусное расстояние" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Focal_length" title="Focal length – Simple English" lang="en-simple" hreflang="en-simple" data-title="Focal length" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Ohniskov%C3%A1_vzdialenos%C5%A5" title="Ohnisková vzdialenosť – Slovak" lang="sk" hreflang="sk" data-title="Ohnisková vzdialenosť" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Gori%C5%A1%C4%8Dna_razdalja" title="Goriščna razdalja – Slovenian" lang="sl" hreflang="sl" data-title="Goriščna razdalja" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/%C5%BDi%C5%BEna_daljina" title="Žižna daljina – Serbian" lang="sr" hreflang="sr" data-title="Žižna daljina" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/%C5%BDari%C5%A1na_duljina" title="Žarišna duljina – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Žarišna duljina" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Polttov%C3%A4li" title="Polttoväli – Finnish" lang="fi" hreflang="fi" data-title="Polttoväli" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Br%C3%A4nnvidd" title="Brännvidd – Swedish" lang="sv" hreflang="sv" data-title="Brännvidd" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-ta mw-list-item"><a href="https://ta.wikipedia.org/wiki/%E0%AE%95%E0%AF%81%E0%AE%B5%E0%AE%BF%E0%AE%AF%E0%AE%A4%E0%AF%8D_%E0%AE%A4%E0%AF%82%E0%AE%B0%E0%AE%AE%E0%AF%8D" title="குவியத் தூரம் – Tamil" lang="ta" hreflang="ta" data-title="குவியத் தூரம்" data-language-autonym="தமிழ்" data-language-local-name="Tamil" class="interlanguage-link-target"><span>தமிழ்</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B8%84%E0%B8%A7%E0%B8%B2%E0%B8%A1%E0%B8%A2%E0%B8%B2%E0%B8%A7%E0%B9%82%E0%B8%9F%E0%B8%81%E0%B8%B1%E0%B8%AA" title="ความยาวโฟกัส – Thai" lang="th" hreflang="th" data-title="ความยาวโฟกัส" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Odak" title="Odak – Turkish" lang="tr" hreflang="tr" data-title="Odak" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%A4%D0%BE%D0%BA%D1%83%D1%81%D0%BD%D0%B0_%D0%B2%D1%96%D0%B4%D1%81%D1%82%D0%B0%D0%BD%D1%8C" title="Фокусна відстань – Ukrainian" lang="uk" hreflang="uk" data-title="Фокусна відстань" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-ur mw-list-item"><a href="https://ur.wikipedia.org/wiki/%D8%B7%D9%88%D9%84_%D9%85%D8%A7%D8%B3%DA%A9%DB%81" title="طول ماسکہ – Urdu" lang="ur" hreflang="ur" data-title="طول ماسکہ" data-language-autonym="اردو" data-language-local-name="Urdu" class="interlanguage-link-target"><span>اردو</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/Ti%C3%AAu_c%E1%BB%B1" title="Tiêu cự – Vietnamese" lang="vi" hreflang="vi" data-title="Tiêu cự" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-zh-yue mw-list-item"><a href="https://zh-yue.wikipedia.org/wiki/%E7%84%A6%E8%B7%9D" title="焦距 – Cantonese" lang="yue" hreflang="yue" data-title="焦距" data-language-autonym="粵語" data-language-local-name="Cantonese" class="interlanguage-link-target"><span>粵語</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E7%84%A6%E8%B7%9D" title="焦距 – Chinese" lang="zh" hreflang="zh" data-title="焦距" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q193540#sitelinks-wikipedia" title="Edit interlanguage links" class="wbc-editpage">Edit links</a></span></div> </div> </div> </div> </header> <div class="vector-page-toolbar"> <div class="vector-page-toolbar-container"> <div id="left-navigation"> <nav aria-label="Namespaces"> <div id="p-associated-pages" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-associated-pages" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-nstab-main" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/Focal_length" title="View the content page [c]" accesskey="c"><span>Article</span></a></li><li id="ca-talk" class="vector-tab-noicon mw-list-item"><a href="/wiki/Talk:Focal_length" rel="discussion" title="Discuss improvements to the content page [t]" accesskey="t"><span>Talk</span></a></li> </ul> </div> </div> <div id="vector-variants-dropdown" class="vector-dropdown emptyPortlet" > <input type="checkbox" id="vector-variants-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-variants-dropdown" class="vector-dropdown-checkbox " aria-label="Change language variant" > <label id="vector-variants-dropdown-label" for="vector-variants-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet" aria-hidden="true" ><span class="vector-dropdown-label-text">English</span> </label> <div class="vector-dropdown-content"> <div id="p-variants" class="vector-menu mw-portlet mw-portlet-variants emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> </div> </div> </nav> </div> <div id="right-navigation" class="vector-collapsible"> <nav aria-label="Views"> <div id="p-views" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-views" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-view" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/Focal_length"><span>Read</span></a></li><li id="ca-edit" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=Focal_length&action=edit" title="Edit this page [e]" accesskey="e"><span>Edit</span></a></li><li id="ca-history" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=Focal_length&action=history" title="Past revisions of this page [h]" accesskey="h"><span>View history</span></a></li> </ul> </div> </div> </nav> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-dropdown" class="vector-dropdown vector-page-tools-dropdown" > <input type="checkbox" id="vector-page-tools-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-tools-dropdown" class="vector-dropdown-checkbox " aria-label="Tools" > <label id="vector-page-tools-dropdown-label" for="vector-page-tools-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet" aria-hidden="true" ><span class="vector-dropdown-label-text">Tools</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-tools-unpinned-container" class="vector-unpinned-container"> <div id="vector-page-tools" class="vector-page-tools vector-pinnable-element"> <div class="vector-pinnable-header vector-page-tools-pinnable-header vector-pinnable-header-unpinned" data-feature-name="page-tools-pinned" data-pinnable-element-id="vector-page-tools" data-pinned-container-id="vector-page-tools-pinned-container" data-unpinned-container-id="vector-page-tools-unpinned-container" > <div class="vector-pinnable-header-label">Tools</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-page-tools.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-page-tools.unpin">hide</button> </div> <div id="p-cactions" class="vector-menu mw-portlet mw-portlet-cactions emptyPortlet vector-has-collapsible-items" title="More options" > <div class="vector-menu-heading"> Actions </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-more-view" class="selected vector-more-collapsible-item mw-list-item"><a href="/wiki/Focal_length"><span>Read</span></a></li><li id="ca-more-edit" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Focal_length&action=edit" title="Edit this page [e]" accesskey="e"><span>Edit</span></a></li><li id="ca-more-history" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Focal_length&action=history"><span>View history</span></a></li> </ul> </div> </div> <div id="p-tb" class="vector-menu mw-portlet mw-portlet-tb" > <div class="vector-menu-heading"> General </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-whatlinkshere" class="mw-list-item"><a href="/wiki/Special:WhatLinksHere/Focal_length" title="List of all English Wikipedia pages containing links to this page [j]" accesskey="j"><span>What links here</span></a></li><li id="t-recentchangeslinked" class="mw-list-item"><a href="/wiki/Special:RecentChangesLinked/Focal_length" rel="nofollow" title="Recent changes in pages linked from this page [k]" accesskey="k"><span>Related changes</span></a></li><li id="t-upload" class="mw-list-item"><a href="//en.wikipedia.org/wiki/Wikipedia:File_Upload_Wizard" title="Upload files [u]" accesskey="u"><span>Upload file</span></a></li><li id="t-permalink" class="mw-list-item"><a href="/w/index.php?title=Focal_length&oldid=1280478286" title="Permanent link to this revision of this page"><span>Permanent link</span></a></li><li id="t-info" class="mw-list-item"><a href="/w/index.php?title=Focal_length&action=info" title="More information about this page"><span>Page information</span></a></li><li id="t-cite" class="mw-list-item"><a href="/w/index.php?title=Special:CiteThisPage&page=Focal_length&id=1280478286&wpFormIdentifier=titleform" title="Information on how to cite this page"><span>Cite this page</span></a></li><li id="t-urlshortener" class="mw-list-item"><a href="/w/index.php?title=Special:UrlShortener&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FFocal_length"><span>Get shortened URL</span></a></li><li id="t-urlshortener-qrcode" class="mw-list-item"><a href="/w/index.php?title=Special:QrCode&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FFocal_length"><span>Download QR code</span></a></li> </ul> </div> </div> <div id="p-coll-print_export" class="vector-menu mw-portlet mw-portlet-coll-print_export" > <div class="vector-menu-heading"> Print/export </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="coll-download-as-rl" class="mw-list-item"><a href="/w/index.php?title=Special:DownloadAsPdf&page=Focal_length&action=show-download-screen" title="Download this page as a PDF file"><span>Download as PDF</span></a></li><li id="t-print" class="mw-list-item"><a href="/w/index.php?title=Focal_length&printable=yes" title="Printable version of this page [p]" accesskey="p"><span>Printable version</span></a></li> </ul> </div> </div> <div id="p-wikibase-otherprojects" class="vector-menu mw-portlet mw-portlet-wikibase-otherprojects" > <div class="vector-menu-heading"> In other projects </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="wb-otherproject-link wb-otherproject-commons mw-list-item"><a href="https://commons.wikimedia.org/wiki/Category:Focal_length" hreflang="en"><span>Wikimedia Commons</span></a></li><li id="t-wikibase" class="wb-otherproject-link wb-otherproject-wikibase-dataitem mw-list-item"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q193540" title="Structured data on this page hosted by Wikidata [g]" accesskey="g"><span>Wikidata item</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> </div> </div> </div> <div class="vector-column-end"> <div class="vector-sticky-pinned-container"> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-pinned-container" class="vector-pinned-container"> </div> </nav> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-pinned-container" class="vector-pinned-container"> <div id="vector-appearance" class="vector-appearance vector-pinnable-element"> <div class="vector-pinnable-header vector-appearance-pinnable-header vector-pinnable-header-pinned" data-feature-name="appearance-pinned" data-pinnable-element-id="vector-appearance" data-pinned-container-id="vector-appearance-pinned-container" data-unpinned-container-id="vector-appearance-unpinned-container" > <div class="vector-pinnable-header-label">Appearance</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-appearance.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Measure of how strongly an optical system converges or diverges light</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">"Rear focal distance" redirects here. For lens to film distance in a camera, see <a href="/wiki/Flange_focal_distance" title="Flange focal distance">Flange focal distance</a>.</div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-More_citations_needed plainlinks metadata ambox ambox-content ambox-Refimprove" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This article <b>needs additional citations for <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verification</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/Focal_length" title="Special:EditPage/Focal length">improve this article</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">adding citations to reliable sources</a>. Unsourced material may be challenged and removed.<br /><small><span class="plainlinks"><i>Find sources:</i> <a rel="nofollow" class="external text" href="https://www.google.com/search?as_eq=wikipedia&q=%22Focal+length%22">"Focal length"</a> – <a rel="nofollow" class="external text" href="https://www.google.com/search?tbm=nws&q=%22Focal+length%22+-wikipedia&tbs=ar:1">news</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?&q=%22Focal+length%22&tbs=bkt:s&tbm=bks">newspapers</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.google.com/search?tbs=bks:1&q=%22Focal+length%22+-wikipedia">books</a> <b>·</b> <a rel="nofollow" class="external text" href="https://scholar.google.com/scholar?q=%22Focal+length%22">scholar</a> <b>·</b> <a rel="nofollow" class="external text" href="https://www.jstor.org/action/doBasicSearch?Query=%22Focal+length%22&acc=on&wc=on">JSTOR</a></span></small></span> <span class="date-container"><i>(<span class="date">November 2021</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Focal-length.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/8b/Focal-length.svg/220px-Focal-length.svg.png" decoding="async" width="220" height="664" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/8b/Focal-length.svg/330px-Focal-length.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/8b/Focal-length.svg/440px-Focal-length.svg.png 2x" data-file-width="512" data-file-height="1545" /></a><figcaption>The <a href="/wiki/Focus_(optics)" title="Focus (optics)">focal point</a> <b>F</b> and focal length <i>f</i> of a positive (convex) <a href="/wiki/Lens" title="Lens">lens</a>, a negative (concave) lens, a <a href="/wiki/Concave_mirror" class="mw-redirect" title="Concave mirror">concave mirror</a>, and a <a href="/wiki/Convex_mirror" class="mw-redirect" title="Convex mirror">convex mirror</a>.</figcaption></figure> <p>The <b>focal length</b> of an <a href="/wiki/Optics" title="Optics">optical</a> system is a measure of how strongly the system converges or diverges <a href="/wiki/Light" title="Light">light</a>; it is the <a href="/wiki/Multiplicative_inverse" title="Multiplicative inverse">inverse</a> of the system's <a href="/wiki/Optical_power" title="Optical power">optical power</a>. A positive focal length indicates that a system <a href="/wiki/Convergence_(optics)" class="mw-redirect" title="Convergence (optics)">converges</a> light, while a negative focal length indicates that the system <a href="/wiki/Divergence_(optics)" class="mw-redirect" title="Divergence (optics)">diverges</a> light. A system with a shorter focal length bends the <a href="/wiki/Ray_(optics)" title="Ray (optics)">rays</a> more sharply, bringing them to a focus in a shorter distance or diverging them more quickly. For the special case of a <a href="/wiki/Thin_lens" title="Thin lens">thin lens</a> in air, a positive focal length is the distance over which initially <a href="/wiki/Collimated_beam" title="Collimated beam">collimated</a> (parallel) rays are brought to a <a href="/wiki/Focus_(optics)" title="Focus (optics)">focus</a>, or alternatively a negative focal length indicates how far in front of the lens a <a href="/wiki/Point_source" title="Point source">point source</a> must be located to form a collimated beam. For more general optical systems, the focal length has no intuitive meaning; it is simply the inverse of the system's optical power. </p><p>In most <a href="/wiki/Photography" title="Photography">photography</a> and all <a href="/wiki/Telescopy" class="mw-redirect" title="Telescopy">telescopy</a>, where the subject is essentially infinitely far away, longer focal length (lower optical power) leads to higher <a href="/wiki/Magnification" title="Magnification">magnification</a> and a narrower <a href="/wiki/Angle_of_view" class="mw-redirect" title="Angle of view">angle of view</a>; conversely, shorter focal length or higher optical power is associated with lower magnification and a wider angle of view. On the other hand, in applications such as <a href="/wiki/Microscopy" title="Microscopy">microscopy</a> in which magnification is achieved by bringing the object close to the lens, a shorter focal length (higher optical power) leads to higher magnification because the subject can be brought closer to the center of projection. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Thin_lens_approximation">Thin lens approximation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Focal_length&action=edit&section=1" title="Edit section: Thin lens approximation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>For a thin lens in air, the focal length is the distance from the center of the <a href="/wiki/Lens_(optics)" class="mw-redirect" title="Lens (optics)">lens</a> to the principal foci (or <i>focal points</i>) of the lens. For a converging lens (for example a <a href="/wiki/Lens_(optics)#Types_of_simple_lenses" class="mw-redirect" title="Lens (optics)">convex lens</a>), the focal length is positive and is the distance at which a beam of <a href="/wiki/Collimated_light" class="mw-redirect" title="Collimated light">collimated light</a> will be focused to a single spot. For a diverging lens (for example a <a href="/wiki/Lens_(optics)#Types_of_simple_lenses" class="mw-redirect" title="Lens (optics)">concave lens</a>), the focal length is negative and is the distance to the point from which a collimated beam appears to be diverging after passing through the lens. </p><p>When a lens is used to form an image of some object, the distance from the object to the lens <i>u</i>, the distance from the lens to the image <i>v</i>, and the focal length <i>f</i> are related by </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\frac {1}{f}}={\frac {1}{u}}+{\frac {1}{v}}\ .}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <mi>f</mi> </mfrac> </mrow> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <mi>u</mi> </mfrac> </mrow> <mo>+</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <mi>v</mi> </mfrac> </mrow> <mtext> </mtext> <mo>.</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\frac {1}{f}}={\frac {1}{u}}+{\frac {1}{v}}\ .}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3667a4f96bd5863e1a007aa89dcc0efc1abed2c7" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.338ex; width:13.445ex; height:5.676ex;" alt="{\displaystyle {\frac {1}{f}}={\frac {1}{u}}+{\frac {1}{v}}\ .}" /></span></dd></dl> <p>The focal length of a thin <i>convex</i> lens can be easily measured by using it to form an image of a distant light source on a screen. The lens is moved until a sharp image is formed on the screen. In this case <style data-mw-deduplicate="TemplateStyles:r1214402035">.mw-parser-output .sfrac{white-space:nowrap}.mw-parser-output .sfrac.tion,.mw-parser-output .sfrac .tion{display:inline-block;vertical-align:-0.5em;font-size:85%;text-align:center}.mw-parser-output .sfrac .num{display:block;line-height:1em;margin:0.0em 0.1em;border-bottom:1px solid}.mw-parser-output .sfrac .den{display:block;line-height:1em;margin:0.1em 0.1em}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den"><i>u</i></span></span>⁠</span> is negligible, and the focal length is then given by </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle f\approx v\ .}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>f</mi> <mo>≈</mo> <mi>v</mi> <mtext> </mtext> <mo>.</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle f\approx v\ .}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/e944e4ed0cd41dcd8e97ca65a147b3bf0fadaf8e" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:6.732ex; height:2.509ex;" alt="{\displaystyle f\approx v\ .}" /></span></dd></dl> <p>Determining the focal length of a <i>concave</i> lens is somewhat more difficult. The focal length of such a lens is defined as the point at which the spreading beams of light meet when they are extended backwards. No image is formed during such a test, and the focal length must be determined by passing light (for example, the light of a laser beam) through the lens, examining how much that light becomes dispersed/ bent, and following the beam of light backwards to the lens's focal point. </p> <div class="mw-heading mw-heading2"><h2 id="General_optical_systems">General optical systems</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Focal_length&action=edit&section=2" title="Edit section: General optical systems"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Thick_Lens_Diagram.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Thick_Lens_Diagram.svg/330px-Thick_Lens_Diagram.svg.png" decoding="async" width="330" height="188" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Thick_Lens_Diagram.svg/495px-Thick_Lens_Diagram.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Thick_Lens_Diagram.svg/660px-Thick_Lens_Diagram.svg.png 2x" data-file-width="621" data-file-height="354" /></a><figcaption>Thick lens diagram</figcaption></figure> <p>For a <i>thick</i> lens (one which has a non-negligible thickness), or an imaging system consisting of several lenses or <a href="/wiki/Curved_mirror" title="Curved mirror">mirrors</a> (e.g. a <a href="/wiki/Photographic_lens" class="mw-redirect" title="Photographic lens">photographic lens</a> or a <a href="/wiki/Telescope" title="Telescope">telescope</a>), there are several related concepts that are referred to as focal lengths: </p> <dl><dt>Effective focal length (EFL)<span class="anchor" id="EFL"></span></dt> <dd>The effective focal length is the inverse of the <a href="/wiki/Optical_power" title="Optical power">optical power</a> of an optical system, and is the value used to calculate the <a href="/wiki/Magnification" title="Magnification">magnification</a> of the system.<sup id="cite_ref-Greivenkamp_1-0" class="reference"><a href="#cite_note-Greivenkamp-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> The imaging properties of the optical system can be modeled by replacing the system with an ideal thin lens with the same EFL.<sup id="cite_ref-efl_2-0" class="reference"><a href="#cite_note-efl-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> The EFL also provides a simple method for finding the <a href="/wiki/Nodal_point" class="mw-redirect" title="Nodal point">nodal points</a> without tracing any rays. It was previously called <i>equivalent focal length</i> (not to be confused with <a href="/wiki/35_mm-equivalent_focal_length" class="mw-redirect" title="35 mm-equivalent focal length">35 mm-equivalent focal length</a>).</dd> <dt>Front focal length (FFL)</dt> <dd>The front focal length <span class="texhtml mvar" style="font-style:italic;">f</span> is the distance from the front focal point <span class="texhtml">F</span> to the front <a href="/wiki/Principal_plane" class="mw-redirect" title="Principal plane">principal plane</a> <span class="texhtml">H</span>.</dd> <dt>Rear focal length (RFL)</dt> <dd>The rear focal length <span class="texhtml mvar" style="font-style:italic;">f<span class="nowrap" style="padding-left:0.15em;">′</span></span> is the distance from the rear principal plane <span class="texhtml">H<span class="nowrap" style="padding-left:0.05em;">′</span></span> to the rear focal point <span class="texhtml">F<span class="nowrap" style="padding-left:0.05em;">′</span></span>.</dd> <dt>Front focal distance (FFD)</dt> <dd>The front focal distance (FFD) (<span class="texhtml"><i>s</i><sub>F</sub></span>) is the distance from the front focal point of the system (<span class="texhtml">F</span>) to the <a href="/wiki/Surface_vertex" class="mw-redirect" title="Surface vertex">vertex</a> of the <i>first optical surface</i> (<span class="texhtml">S<sub>1</sub></span>).<sup id="cite_ref-Greivenkamp_1-1" class="reference"><a href="#cite_note-Greivenkamp-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Hecht1_3-0" class="reference"><a href="#cite_note-Hecht1-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> Some authors refer to this as "front focal length".</dd> <dt>Back focal distance (BFD)</dt> <dd>Back focal distance (BFD) (<span class="texhtml"><i>s<span class="nowrap" style="padding-left:0.05em;">′</span></i><sub>F<span class="nowrap" style="padding-left:0.05em;">′</span></sub></span>) is the distance from the vertex of the <i>last optical surface</i> of the system (<span class="texhtml">S<sub>2</sub></span>) to the rear focal point (<span class="texhtml">F<span class="nowrap" style="padding-left:0.05em;">′</span></span>).<sup id="cite_ref-Greivenkamp_1-2" class="reference"><a href="#cite_note-Greivenkamp-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Hecht1_3-1" class="reference"><a href="#cite_note-Hecht1-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> Some authors refer to this as "back focal length".</dd></dl> <p>For an optical system in air the effective focal length, front focal length, and rear focal length are all the same and may be called simply "focal length". </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Wiki_efl.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Wiki_efl.jpg/250px-Wiki_efl.jpg" decoding="async" width="220" height="198" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Wiki_efl.jpg/330px-Wiki_efl.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Wiki_efl.jpg/500px-Wiki_efl.jpg 2x" data-file-width="1192" data-file-height="1072" /></a><figcaption>Sketch of human eye showing rear focal length <span class="texhtml">f<span class="nowrap" style="padding-left:0.15em;">′</span></span> and EFL</figcaption></figure> <p>For an optical system in a medium other than air or vacuum, the front and rear focal lengths are equal to the EFL times the <a href="/wiki/Refractive_index" title="Refractive index">refractive index</a> of the medium in front of or behind the lens (<span class="texhtml"><i>n</i><sub>1</sub></span> and <span class="texhtml"><i>n</i><sub>2</sub></span> in the diagram above). The term "focal length" by itself is ambiguous in this case. The historical usage was to define the "focal length" as the EFL times the index of refraction of the medium.<sup id="cite_ref-efl_2-1" class="reference"><a href="#cite_note-efl-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Nodal_4-0" class="reference"><a href="#cite_note-Nodal-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> For a system with different media on both sides, such as the human eye, the front and rear focal lengths are not equal to one another, and convention may dictate which one is called "the focal length" of the system. Some modern authors avoid this ambiguity by instead defining "focal length" to be a synonym for EFL.<sup id="cite_ref-Greivenkamp_1-3" class="reference"><a href="#cite_note-Greivenkamp-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p><p>The distinction between front/rear focal length and EFL is important for studying the human eye. The eye can be represented by an equivalent thin lens at an air/fluid boundary with front and rear focal lengths equal to those of the eye, or it can be represented by a <em>different</em> equivalent thin lens that is totally in air, with focal length equal to the eye's EFL. </p><p>For the case of a lens of thickness <span class="texhtml mvar" style="font-style:italic;">d</span> in air (<span class="texhtml"><i>n</i><sub>1</sub> = <i>n</i><sub>2</sub> = 1</span>), and surfaces with <a href="/wiki/Radius_of_curvature_(optics)" title="Radius of curvature (optics)">radii of curvature</a> <span class="texhtml"><i>R</i><sub>1</sub></span> and <span class="texhtml"><i>R</i><sub>2</sub></span>, the effective focal length <span class="texhtml mvar" style="font-style:italic;">f</span> is given by the <a href="/wiki/Lensmaker%27s_equation" class="mw-redirect" title="Lensmaker's equation">Lensmaker's equation</a>:<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p><p><span class="mwe-math-element"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\frac {1}{f}}=(n-1)\left({\frac {1}{R_{1}}}-{\frac {1}{R_{2}}}+{\frac {(n-1)d}{nR_{1}R_{2}}}\right),}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <mi>f</mi> </mfrac> </mrow> <mo>=</mo> <mo stretchy="false">(</mo> <mi>n</mi> <mo>−</mo> <mn>1</mn> <mo stretchy="false">)</mo> <mrow> <mo>(</mo> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <msub> <mi>R</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> </mfrac> </mrow> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <msub> <mi>R</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> </mfrac> </mrow> <mo>+</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mo stretchy="false">(</mo> <mi>n</mi> <mo>−</mo> <mn>1</mn> <mo stretchy="false">)</mo> <mi>d</mi> </mrow> <mrow> <mi>n</mi> <msub> <mi>R</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> <msub> <mi>R</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> </mrow> </mfrac> </mrow> </mrow> <mo>)</mo> </mrow> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\frac {1}{f}}=(n-1)\left({\frac {1}{R_{1}}}-{\frac {1}{R_{2}}}+{\frac {(n-1)d}{nR_{1}R_{2}}}\right),}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b2e2010210e076991723978c5a99360eeed59472" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:39.511ex; height:6.343ex;" alt="{\displaystyle {\frac {1}{f}}=(n-1)\left({\frac {1}{R_{1}}}-{\frac {1}{R_{2}}}+{\frac {(n-1)d}{nR_{1}R_{2}}}\right),}" /></span>where <span class="texhtml mvar" style="font-style:italic;">n</span> is the refractive index of the lens medium. The quantity <span class="texhtml"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035" /><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den"><i>f</i></span></span>⁠</span></span> is also known as the <a href="/wiki/Optical_power" title="Optical power">optical power</a> of the lens. </p><p>The corresponding front focal distance is:<sup id="cite_ref-Hecht2_6-0" class="reference"><a href="#cite_note-Hecht2-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup><span class="mwe-math-element"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\mbox{FFD}}=f\left(1+{\frac {(n-1)d}{nR_{2}}}\right),}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <mtext>FFD</mtext> </mstyle> </mrow> <mo>=</mo> <mi>f</mi> <mrow> <mo>(</mo> <mrow> <mn>1</mn> <mo>+</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mo stretchy="false">(</mo> <mi>n</mi> <mo>−</mo> <mn>1</mn> <mo stretchy="false">)</mo> <mi>d</mi> </mrow> <mrow> <mi>n</mi> <msub> <mi>R</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> </mrow> </mfrac> </mrow> </mrow> <mo>)</mo> </mrow> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\mbox{FFD}}=f\left(1+{\frac {(n-1)d}{nR_{2}}}\right),}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/9471eb9177d72521a5943bfa14a7756f31289910" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:27.292ex; height:6.343ex;" alt="{\displaystyle {\mbox{FFD}}=f\left(1+{\frac {(n-1)d}{nR_{2}}}\right),}" /></span> and the back focal distance: <span class="mwe-math-element"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\mbox{BFD}}=f\left(1-{\frac {(n-1)d}{nR_{1}}}\right).}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <mtext>BFD</mtext> </mstyle> </mrow> <mo>=</mo> <mi>f</mi> <mrow> <mo>(</mo> <mrow> <mn>1</mn> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mo stretchy="false">(</mo> <mi>n</mi> <mo>−</mo> <mn>1</mn> <mo stretchy="false">)</mo> <mi>d</mi> </mrow> <mrow> <mi>n</mi> <msub> <mi>R</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> </mrow> </mfrac> </mrow> </mrow> <mo>)</mo> </mrow> <mo>.</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\mbox{BFD}}=f\left(1-{\frac {(n-1)d}{nR_{1}}}\right).}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0d960246575820798485bd311f6821f03f3fa973" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:27.42ex; height:6.343ex;" alt="{\displaystyle {\mbox{BFD}}=f\left(1-{\frac {(n-1)d}{nR_{1}}}\right).}" /></span> </p><p>In the <a href="/wiki/Radius_of_curvature_(optics)" title="Radius of curvature (optics)">sign convention</a> used here, the value of <span class="texhtml"><i>R</i><sub>1</sub></span> will be positive if the first lens surface is convex, and negative if it is concave. The value of <span class="texhtml"><i>R</i><sub>2</sub></span> is negative if the second surface is convex, and positive if concave. Sign conventions vary between different authors, which results in different forms of these equations depending on the convention used. </p><p>For a <a href="/wiki/Curved_mirror" title="Curved mirror">spherically-curved mirror</a> in air, the magnitude of the focal length is equal to the <a href="/wiki/Radius_of_curvature_(optics)" title="Radius of curvature (optics)">radius of curvature</a> of the mirror divided by two. The focal length is positive for a concave mirror, and negative for a convex mirror. In the sign convention used in optical design, a concave mirror has negative radius of curvature, so </p><p><span class="mwe-math-element"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle f=-{R \over 2},}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>f</mi> <mo>=</mo> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi>R</mi> <mn>2</mn> </mfrac> </mrow> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle f=-{R \over 2},}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5be974ce82b40e2c9b3c401cfe0df8aee8b17b7b" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:9.432ex; height:5.176ex;" alt="{\displaystyle f=-{R \over 2},}" /></span> </p><p>where <span class="texhtml mvar" style="font-style:italic;">R</span> is the radius of curvature of the mirror's surface. </p><p>See <a href="/wiki/Radius_of_curvature_(optics)" title="Radius of curvature (optics)">Radius of curvature (optics)</a> for more information on the sign convention for radius of curvature used here. </p> <div class="mw-heading mw-heading2"><h2 id="In_photography">In photography</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Focal_length&action=edit&section=3" title="Edit section: In photography"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1273380762/mw-parser-output/.tmulti">.mw-parser-output .tmulti .multiimageinner{display:flex;flex-direction:column}.mw-parser-output .tmulti .trow{display:flex;flex-direction:row;clear:left;flex-wrap:wrap;width:100%;box-sizing:border-box}.mw-parser-output .tmulti .tsingle{margin:1px;float:left}.mw-parser-output .tmulti .theader{clear:both;font-weight:bold;text-align:center;align-self:center;background-color:transparent;width:100%}.mw-parser-output .tmulti .thumbcaption{background-color:transparent}.mw-parser-output .tmulti .text-align-left{text-align:left}.mw-parser-output .tmulti .text-align-right{text-align:right}.mw-parser-output .tmulti .text-align-center{text-align:center}@media all and (max-width:720px){.mw-parser-output .tmulti .thumbinner{width:100%!important;box-sizing:border-box;max-width:none!important;align-items:center}.mw-parser-output .tmulti .trow{justify-content:center}.mw-parser-output .tmulti .tsingle{float:none!important;max-width:100%!important;box-sizing:border-box;text-align:center}.mw-parser-output .tmulti .tsingle .thumbcaption{text-align:left}.mw-parser-output .tmulti .trow>.thumbcaption{text-align:center}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}</style><div class="thumb tmulti tnone center"><div class="thumbinner multiimageinner" style="width:616px;max-width:616px"><div class="trow"><div class="tsingle" style="width:152px;max-width:152px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Angleofview_28mm_f4.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/1/12/Angleofview_28mm_f4.jpg/150px-Angleofview_28mm_f4.jpg" decoding="async" width="150" height="98" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/12/Angleofview_28mm_f4.jpg/225px-Angleofview_28mm_f4.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/1/12/Angleofview_28mm_f4.jpg 2x" data-file-width="298" data-file-height="195" /></a></span></div><div class="thumbcaption">28 mm lens</div></div><div class="tsingle" style="width:152px;max-width:152px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Angleofview_50mm_f4.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/9/9c/Angleofview_50mm_f4.jpg/250px-Angleofview_50mm_f4.jpg" decoding="async" width="150" height="96" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/9/9c/Angleofview_50mm_f4.jpg 2x" data-file-width="300" data-file-height="192" /></a></span></div><div class="thumbcaption">50 mm lens</div></div><div class="tsingle" style="width:152px;max-width:152px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Angleofview_70mm_f4.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/6/68/Angleofview_70mm_f4.jpg/250px-Angleofview_70mm_f4.jpg" decoding="async" width="150" height="96" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/6/68/Angleofview_70mm_f4.jpg 2x" data-file-width="300" data-file-height="191" /></a></span></div><div class="thumbcaption">70 mm lens</div></div><div class="tsingle" style="width:152px;max-width:152px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Angleofview_210mm_f4.jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/f/fd/Angleofview_210mm_f4.jpg/250px-Angleofview_210mm_f4.jpg" decoding="async" width="150" height="98" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/f/fd/Angleofview_210mm_f4.jpg 2x" data-file-width="300" data-file-height="195" /></a></span></div><div class="thumbcaption">210 mm lens</div></div></div><div class="trow" style="display:flow-root"><div class="thumbcaption" style="text-align:center">An example of how lens choice affects angle of view. The photos above were taken by a <a href="/wiki/135_film" title="135 film">35 mm</a> camera at a fixed distance from the subject.</div></div></div></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Thin_lens_images.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/47/Thin_lens_images.svg/330px-Thin_lens_images.svg.png" decoding="async" width="330" height="189" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/47/Thin_lens_images.svg/495px-Thin_lens_images.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/47/Thin_lens_images.svg/660px-Thin_lens_images.svg.png 2x" data-file-width="512" data-file-height="293" /></a><figcaption>Images of black letters in a thin convex lens of focal length <span class="texhtml mvar" style="font-style:italic;">f</span> are shown in red. Selected rays are shown for letters <b>E</b>, <b>I</b> and <b>K</b> in blue, green and orange, respectively. <b>E</b> (at <span class="texhtml">2<i>f</i></span>) has an equal-size, real and inverted image; <b>I</b> (at <span class="texhtml mvar" style="font-style:italic;">f</span>) has its image at infinity; and <b>K</b> (at <span class="texhtml"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035" /><span class="sfrac">⁠<span class="tion"><span class="num"><i>f</i></span><span class="sr-only">/</span><span class="den">2</span></span>⁠</span></span>) has a double-size, virtual and upright image.</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Camera_focal_length_distance_house_animation.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/d/d3/Camera_focal_length_distance_house_animation.gif/330px-Camera_focal_length_distance_house_animation.gif" decoding="async" width="330" height="330" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/d3/Camera_focal_length_distance_house_animation.gif/500px-Camera_focal_length_distance_house_animation.gif 1.5x, //upload.wikimedia.org/wikipedia/commons/d/d3/Camera_focal_length_distance_house_animation.gif 2x" data-file-width="512" data-file-height="512" /></a><figcaption>In this computer simulation, adjusting the field of view (by changing the focal length) while keeping the subject in frame (by changing accordingly the position of the camera) results in vastly differing images. At focal lengths approaching infinity (0 degrees of angle of view), the light rays are nearly parallel to each other, resulting in the subject looking "flattened". At small focal lengths (bigger field of view), the subject appears "foreshortened".</figcaption></figure> <p>Camera lens focal lengths are usually specified in millimetres (mm), but some older lenses are marked in centimetres (cm) or inches. </p><p>Focal length <span style="padding-right:0.15em;">(</span><span class="texhtml mvar" style="font-style:italic;">f</span><span style="padding-left:0.15em;">)</span> and <a href="/wiki/Field_of_view" title="Field of view">field of view</a> (FOV) of a lens are inversely proportional. For a standard <a href="/wiki/Rectilinear_lens" title="Rectilinear lens">rectilinear lens</a>, <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\textstyle \mathrm {FOV} =2\arctan {\left({x \over 2f}\right)}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">F</mi> <mi mathvariant="normal">O</mi> <mi mathvariant="normal">V</mi> </mrow> <mo>=</mo> <mn>2</mn> <mi>arctan</mi> <mo>⁡</mo> <mrow class="MJX-TeXAtom-ORD"> <mrow> <mo>(</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mi>x</mi> <mrow> <mn>2</mn> <mi>f</mi> </mrow> </mfrac> </mrow> <mo>)</mo> </mrow> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\textstyle \mathrm {FOV} =2\arctan {\left({x \over 2f}\right)}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/9fadaccca3e807de1b06fee1330bf6fd9a6ce510" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:21.908ex; height:4.843ex;" alt="{\textstyle \mathrm {FOV} =2\arctan {\left({x \over 2f}\right)}}" /></span>, where <span class="texhtml mvar" style="font-style:italic;">x</span> is the width of the film or imaging sensor. </p><p>When a photographic lens is set to "infinity", its rear <a href="/wiki/Principal_plane" class="mw-redirect" title="Principal plane">principal plane</a> is separated from the sensor or film, which is then situated at the <a href="/wiki/Focal_plane" class="mw-redirect" title="Focal plane">focal plane</a>, by the lens's focal length. Objects far away from the camera then produce sharp images on the sensor or film, which is also at the image plane. </p><p>To render closer objects in sharp focus, the lens must be adjusted to increase the distance between the rear principal plane and the film, to put the film at the image plane. The focal length <span class="texhtml mvar" style="font-style:italic;">f</span>, the distance from the front principal plane to the object to photograph <span class="texhtml"><i>s</i><sub>1</sub></span>, and the distance from the rear principal plane to the image plane <span class="texhtml"><i>s</i><sub>2</sub></span> are then related by: </p><p><span class="mwe-math-element"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\frac {1}{s_{1}}}+{\frac {1}{s_{2}}}={\frac {1}{f}}\,.}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <msub> <mi>s</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>1</mn> </mrow> </msub> </mfrac> </mrow> <mo>+</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <msub> <mi>s</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msub> </mfrac> </mrow> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <mi>f</mi> </mfrac> </mrow> <mspace width="thinmathspace"></mspace> <mo>.</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\frac {1}{s_{1}}}+{\frac {1}{s_{2}}}={\frac {1}{f}}\,.}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/cc44b7db40d427d83ab486775171abc4d2d9b2b0" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.338ex; width:15.049ex; height:5.676ex;" alt="{\displaystyle {\frac {1}{s_{1}}}+{\frac {1}{s_{2}}}={\frac {1}{f}}\,.}" /></span> </p><p>As <span class="texhtml"><i>s</i><sub>1</sub></span> is decreased, <span class="texhtml"><i>s</i><sub>2</sub></span> must be increased. For example, consider a <a href="/wiki/Normal_lens" title="Normal lens">normal lens</a> for a <a href="/wiki/35mm_format" class="mw-redirect" title="35mm format">35 mm</a> camera with a focal length of <span class="texhtml"><i>f</i> =</span> 50 mm. To focus a distant object (<span class="texhtml"><i>s</i><sub>1</sub> ≈ ∞</span>), the rear principal plane of the lens must be located a distance <span class="texhtml"><i>s</i><sub>2</sub> =</span> 50 mm from the film plane, so that it is at the location of the image plane. To focus an object 1 m away (<span class="texhtml"><i>s</i><sub>1</sub> =</span> 1,000 mm), the lens must be moved 2.6 mm farther away from the film plane, to <span class="texhtml"><i>s</i><sub>2</sub> =</span> 52.6 mm. </p><p>The focal length of a lens determines the magnification at which it images distant objects. It is equal to the distance between the image plane and a <a href="/wiki/Pinhole_camera" title="Pinhole camera">pinhole that images</a> distant objects the same size as the lens in question. For <a href="/wiki/Rectilinear_lens" title="Rectilinear lens">rectilinear lenses</a> (that is, with no <a href="/wiki/Image_distortion" class="mw-redirect" title="Image distortion">image distortion</a>), the imaging of distant objects is well modelled as a <a href="/wiki/Pinhole_camera_model" title="Pinhole camera model">pinhole camera model</a>.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> This model leads to the simple geometric model that photographers use for computing the <a href="/wiki/Angle_of_view" class="mw-redirect" title="Angle of view">angle of view</a> of a camera; in this case, the angle of view depends only on the ratio of focal length to <a href="/wiki/Film_format" title="Film format">film size</a>. In general, the angle of view depends also on the distortion.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p><p>A lens with a focal length about equal to the diagonal size of the film or sensor format is known as a <a href="/wiki/Normal_lens" title="Normal lens">normal lens</a>; its angle of view is similar to the angle subtended by a large-enough print viewed at a typical viewing distance of the print diagonal, which therefore yields a normal perspective when viewing the print;<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> this angle of view is about 53 degrees diagonally. For <a href="/wiki/Full-frame_digital_SLR" class="mw-redirect" title="Full-frame digital SLR">full-frame</a> 35 mm-format cameras, the diagonal is 43 mm and a typical "normal" lens has a 50 mm focal length. A lens with a focal length shorter than normal is often referred to as a <a href="/wiki/Wide-angle_lens" title="Wide-angle lens">wide-angle lens</a> (typically 35 mm and less, for 35 mm-format cameras), while a lens significantly longer than normal may be referred to as a <a href="/wiki/Telephoto_lens" title="Telephoto lens">telephoto lens</a> (typically 85 mm and more, for 35 mm-format cameras). Technically, long focal length lenses are only "telephoto" if the focal length is longer than the physical length of the lens, but the term is often used to describe any long focal length lens. </p><p>Due to the popularity of the <a href="/wiki/135_film" title="135 film">35 mm standard</a>, camera–lens combinations are often described in terms of their 35 mm-equivalent focal length, that is, the focal length of a lens that would have the same angle of view, or field of view, if used on a full-frame 35 mm camera. Use of a 35 mm-equivalent focal length is particularly common with <a href="/wiki/Digital_camera" title="Digital camera">digital cameras</a>, which often use sensors smaller than 35 mm film, and so require correspondingly shorter focal lengths to achieve a given angle of view, by a factor known as the <a href="/wiki/Crop_factor" title="Crop factor">crop factor</a>. </p> <div class="mw-heading mw-heading2"><h2 id="Optical_power">Optical power</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Focal_length&action=edit&section=4" title="Edit section: Optical power"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Optical_power_of_a_lens.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7d/Optical_power_of_a_lens.svg/220px-Optical_power_of_a_lens.svg.png" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7d/Optical_power_of_a_lens.svg/330px-Optical_power_of_a_lens.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/7d/Optical_power_of_a_lens.svg/440px-Optical_power_of_a_lens.svg.png 2x" data-file-width="512" data-file-height="384" /></a><figcaption>Illustration of the relationship between optical power and focal length</figcaption></figure> <p>The <a href="/wiki/Optical_power" title="Optical power">optical power</a> of a <a href="/wiki/Lens_(optics)" class="mw-redirect" title="Lens (optics)">lens</a> or curved <a href="/wiki/Mirror" title="Mirror">mirror</a> is a <a href="/wiki/Physical_quantity" title="Physical quantity">physical quantity</a> equal to the <a href="/wiki/Multiplicative_inverse" title="Multiplicative inverse">reciprocal</a> of the focal length, expressed in <a href="/wiki/Metre" title="Metre">metres</a>. A <a href="/wiki/Dioptre" title="Dioptre">dioptre</a> is its <a href="/wiki/Unit_of_measurement" title="Unit of measurement">unit of measurement</a> with <a href="/wiki/Dimension_(physics)" class="mw-redirect" title="Dimension (physics)">dimension</a> of <a href="/wiki/Reciprocal_length" title="Reciprocal length">reciprocal length</a>, equivalent to one <a href="/wiki/Reciprocal_metre" class="mw-redirect" title="Reciprocal metre">reciprocal metre</a>, 1 dioptre = 1 m<sup>−1</sup>. For example, a 2-dioptre lens brings parallel <a href="/wiki/Ray_(optics)" title="Ray (optics)">rays</a> of light to focus at <style data-mw-deduplicate="TemplateStyles:r1154941027">.mw-parser-output .frac{white-space:nowrap}.mw-parser-output .frac .num,.mw-parser-output .frac .den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output .frac .den{vertical-align:sub}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style><span class="frac"><span class="num">1</span>⁄<span class="den">2</span></span> metre. A flat window has an optical power of zero dioptres, as it does not cause light to converge or diverge.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p><p>The main benefit of using optical power rather than focal length is that the <a href="/wiki/Thin_lens_formula" class="mw-redirect" title="Thin lens formula">thin lens formula</a> has the object distance, image distance, and focal length all as reciprocals. Additionally, when <a href="/wiki/Thin_lens" title="Thin lens">relatively thin lenses</a> are placed close together their powers approximately add. Thus, a thin 2.0-dioptre lens placed close to a thin 0.5-dioptre lens yields almost the same focal length as a single 2.5-dioptre lens. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Focal_length&action=edit&section=5" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Depth_of_field" title="Depth of field">Depth of field</a></li> <li><a href="/wiki/Dioptre" title="Dioptre">Dioptre</a></li> <li><a href="/wiki/F-number" title="F-number">f-number</a> or focal ratio</li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Focal_length&action=edit&section=6" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output .side-box-image{padding:2px 0 2px 0.9em;text-align:center}.mw-parser-output .side-box-imageright{padding:2px 0.9em 2px 0;text-align:center}@media(min-width:500px){.mw-parser-output .side-box-flex{display:flex;align-items:center}.mw-parser-output .side-box-text{flex:1;min-width:0}}@media(min-width:720px){.mw-parser-output .side-box{width:238px}.mw-parser-output .side-box-right{clear:right;float:right;margin-left:1em}.mw-parser-output .side-box-left{margin-right:1em}}</style><style data-mw-deduplicate="TemplateStyles:r1237033735">@media print{body.ns-0 .mw-parser-output .sistersitebox{display:none!important}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}</style><div class="side-box side-box-right plainlinks sistersitebox"><style data-mw-deduplicate="TemplateStyles:r1126788409">.mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0}</style> <div class="side-box-flex"> <div class="side-box-image"><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Commons-logo.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/40px-Commons-logo.svg.png" decoding="async" width="30" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/60px-Commons-logo.svg.png 1.5x" data-file-width="1024" data-file-height="1376" /></a></span></div> <div class="side-box-text plainlist">Wikimedia Commons has media related to <span style="font-weight: bold; font-style: italic;"><a href="https://commons.wikimedia.org/wiki/Category:Focal_length" class="extiw" title="commons:Category:Focal length">Focal length</a></span>.</div></div> </div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-Greivenkamp-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-Greivenkamp_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Greivenkamp_1-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Greivenkamp_1-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Greivenkamp_1-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFGrievenkamp2004" class="citation book cs1">Grievenkamp, John E. (2004). <i>Field Guide to Geometrical Optics</i>. <a href="/wiki/SPIE_Press" class="mw-redirect" title="SPIE Press">SPIE Press</a>. pp. <span class="nowrap">6–</span>9. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-8194-5294-8" title="Special:BookSources/978-0-8194-5294-8"><bdi>978-0-8194-5294-8</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Field+Guide+to+Geometrical+Optics&rft.pages=%3Cspan+class%3D%22nowrap%22%3E6-%3C%2Fspan%3E9&rft.pub=SPIE+Press&rft.date=2004&rft.isbn=978-0-8194-5294-8&rft.aulast=Grievenkamp&rft.aufirst=John+E.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFocal+length" class="Z3988"></span></span> </li> <li id="cite_note-efl-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-efl_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-efl_2-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFSimpson2023" class="citation journal cs1">Simpson, Michael J. (24 February 2023). "Focal Length, EFL, and the Eye". <i>Applied Optics</i>. <b>62</b> (7): <span class="nowrap">1853–</span>1857. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2023ApOpt..62.1853S">2023ApOpt..62.1853S</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1364%2FAO.481805">10.1364/AO.481805</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/37132938">37132938</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Applied+Optics&rft.atitle=Focal+Length%2C+EFL%2C+and+the+Eye&rft.volume=62&rft.issue=7&rft.pages=%3Cspan+class%3D%22nowrap%22%3E1853-%3C%2Fspan%3E1857&rft.date=2023-02-24&rft_id=info%3Apmid%2F37132938&rft_id=info%3Adoi%2F10.1364%2FAO.481805&rft_id=info%3Abibcode%2F2023ApOpt..62.1853S&rft.aulast=Simpson&rft.aufirst=Michael+J.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFocal+length" class="Z3988"></span></span> </li> <li id="cite_note-Hecht1-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-Hecht1_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Hecht1_3-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFHecht2002" class="citation book cs1">Hecht, Eugene (2002). <i>Optics</i> (4th ed.). <a href="/wiki/Addison_Wesley" class="mw-redirect" title="Addison Wesley">Addison Wesley</a>. p. 168. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0805385663" title="Special:BookSources/978-0805385663"><bdi>978-0805385663</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Optics&rft.pages=168&rft.edition=4th&rft.pub=Addison+Wesley&rft.date=2002&rft.isbn=978-0805385663&rft.aulast=Hecht&rft.aufirst=Eugene&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFocal+length" class="Z3988"></span></span> </li> <li id="cite_note-Nodal-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-Nodal_4-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFSimpson2022" class="citation journal cs1">Simpson, Michael J. (28 March 2022). "Nodal points and the eye". <i>Applied Optics</i>. <b>61</b> (10): <span class="nowrap">2797–</span>2804. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2022ApOpt..61.2797S">2022ApOpt..61.2797S</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1364%2FAO.455464">10.1364/AO.455464</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/35471355">35471355</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Applied+Optics&rft.atitle=Nodal+points+and+the+eye&rft.volume=61&rft.issue=10&rft.pages=%3Cspan+class%3D%22nowrap%22%3E2797-%3C%2Fspan%3E2804&rft.date=2022-03-28&rft_id=info%3Apmid%2F35471355&rft_id=info%3Adoi%2F10.1364%2FAO.455464&rft_id=info%3Abibcode%2F2022ApOpt..61.2797S&rft.aulast=Simpson&rft.aufirst=Michael+J.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFocal+length" class="Z3988"></span></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFHecht2017" class="citation book cs1">Hecht, Eugene (2017). "6.1 thick Lenses and Lens systems". <i>Optics</i> (5th ed.). Pearson. p. 257. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-292-09693-3" title="Special:BookSources/978-1-292-09693-3"><bdi>978-1-292-09693-3</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=6.1+thick+Lenses+and+Lens+systems&rft.btitle=Optics&rft.pages=257&rft.edition=5th&rft.pub=Pearson&rft.date=2017&rft.isbn=978-1-292-09693-3&rft.aulast=Hecht&rft.aufirst=Eugene&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFocal+length" class="Z3988"></span></span> </li> <li id="cite_note-Hecht2-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-Hecht2_6-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFHecht2002" class="citation book cs1">Hecht, Eugene (2002). <i>Optics</i> (4th ed.). <a href="/wiki/Addison_Wesley" class="mw-redirect" title="Addison Wesley">Addison Wesley</a>. pp. <span class="nowrap">244–</span>245. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0805385663" title="Special:BookSources/978-0805385663"><bdi>978-0805385663</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Optics&rft.pages=%3Cspan+class%3D%22nowrap%22%3E244-%3C%2Fspan%3E245&rft.edition=4th&rft.pub=Addison+Wesley&rft.date=2002&rft.isbn=978-0805385663&rft.aulast=Hecht&rft.aufirst=Eugene&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFocal+length" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFCharles2000" class="citation book cs1">Charles, Jeffrey (2000). <span class="id-lock-registration" title="Free registration required"><a rel="nofollow" class="external text" href="https://archive.org/details/practicalastroph00char"><i>Practical astrophotography</i></a></span>. Springer. pp. <a rel="nofollow" class="external text" href="https://archive.org/details/practicalastroph00char/page/63">63</a>–66. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-85233-023-1" title="Special:BookSources/978-1-85233-023-1"><bdi>978-1-85233-023-1</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Practical+astrophotography&rft.pages=63-66&rft.pub=Springer&rft.date=2000&rft.isbn=978-1-85233-023-1&rft.aulast=Charles&rft.aufirst=Jeffrey&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fpracticalastroph00char&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFocal+length" class="Z3988"></span></span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFStroebelZakia1993" class="citation book cs1">Stroebel, Leslie; Zakia, Richard D. (1993). <span class="id-lock-registration" title="Free registration required"><a rel="nofollow" class="external text" href="https://archive.org/details/focalencyclopedi00lesl"><i>The Focal encyclopedia of photography</i></a></span> (3rd ed.). <a href="/wiki/Focal_Press" title="Focal Press">Focal Press</a>. p. <a rel="nofollow" class="external text" href="https://archive.org/details/focalencyclopedi00lesl/page/27">27</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-240-51417-8" title="Special:BookSources/978-0-240-51417-8"><bdi>978-0-240-51417-8</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Focal+encyclopedia+of+photography&rft.pages=27&rft.edition=3rd&rft.pub=Focal+Press&rft.date=1993&rft.isbn=978-0-240-51417-8&rft.aulast=Stroebel&rft.aufirst=Leslie&rft.au=Zakia%2C+Richard+D.&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Ffocalencyclopedi00lesl&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFocal+length" class="Z3988"></span></span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFStroebel1999" class="citation book cs1">Stroebel, Leslie D. (1999). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=71zxDuunAvMC&q=appear-normal+focal-length-lens+print-size+diagonal+viewer+distance&pg=PA136"><i>View Camera Technique</i></a>. <a href="/wiki/Focal_Press" title="Focal Press">Focal Press</a>. pp. <span class="nowrap">135–</span>138. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-240-80345-6" title="Special:BookSources/978-0-240-80345-6"><bdi>978-0-240-80345-6</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=View+Camera+Technique&rft.pages=%3Cspan+class%3D%22nowrap%22%3E135-%3C%2Fspan%3E138&rft.pub=Focal+Press&rft.date=1999&rft.isbn=978-0-240-80345-6&rft.aulast=Stroebel&rft.aufirst=Leslie+D.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3D71zxDuunAvMC%26q%3Dappear-normal%2Bfocal-length-lens%2Bprint-size%2Bdiagonal%2Bviewer%2Bdistance%26pg%3DPA136&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFocal+length" class="Z3988"></span></span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFGreivenkamp2004" class="citation book cs1">Greivenkamp, John E. (2004). <i>Field Guide to Geometrical Optics</i>. SPIE Field Guides vol. <b>FG01</b>. SPIE. p. 7. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-8194-5294-7" title="Special:BookSources/0-8194-5294-7"><bdi>0-8194-5294-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Field+Guide+to+Geometrical+Optics&rft.pages=7&rft.pub=SPIE&rft.date=2004&rft.isbn=0-8194-5294-7&rft.aulast=Greivenkamp&rft.aufirst=John+E.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AFocal+length" class="Z3988"></span></span> </li> </ol></div></div> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:": "}.mw-parser-output .hlist dd::after,.mw-parser-output .hlist li::after{content:" · ";font-weight:bold}.mw-parser-output .hlist dd:last-child::after,.mw-parser-output .hlist dt:last-child::after,.mw-parser-output .hlist li:last-child::after{content:none}.mw-parser-output .hlist dd dd:first-child::before,.mw-parser-output .hlist dd dt:first-child::before,.mw-parser-output .hlist dd li:first-child::before,.mw-parser-output .hlist dt dd:first-child::before,.mw-parser-output .hlist dt dt:first-child::before,.mw-parser-output .hlist dt li:first-child::before,.mw-parser-output .hlist li dd:first-child::before,.mw-parser-output .hlist li dt:first-child::before,.mw-parser-output .hlist li li:first-child::before{content:" (";font-weight:normal}.mw-parser-output .hlist dd dd:last-child::after,.mw-parser-output .hlist dd dt:last-child::after,.mw-parser-output .hlist dd li:last-child::after,.mw-parser-output .hlist dt dd:last-child::after,.mw-parser-output .hlist dt dt:last-child::after,.mw-parser-output .hlist dt li:last-child::after,.mw-parser-output .hlist li dd:last-child::after,.mw-parser-output .hlist li dt:last-child::after,.mw-parser-output .hlist li li:last-child::after{content:")";font-weight:normal}.mw-parser-output .hlist ol{counter-reset:listitem}.mw-parser-output .hlist ol>li{counter-increment:listitem}.mw-parser-output .hlist ol>li::before{content:" "counter(listitem)"\a0 "}.mw-parser-output .hlist dd ol>li:first-child::before,.mw-parser-output .hlist dt ol>li:first-child::before,.mw-parser-output .hlist li ol>li:first-child::before{content:" ("counter(listitem)"\a0 "}</style><style data-mw-deduplicate="TemplateStyles:r1236075235">.mw-parser-output .navbox{box-sizing:border-box;border:1px solid #a2a9b1;width:100%;clear:both;font-size:88%;text-align:center;padding:1px;margin:1em auto 0}.mw-parser-output .navbox .navbox{margin-top:0}.mw-parser-output .navbox+.navbox,.mw-parser-output .navbox+.navbox-styles+.navbox{margin-top:-1px}.mw-parser-output .navbox-inner,.mw-parser-output .navbox-subgroup{width:100%}.mw-parser-output .navbox-group,.mw-parser-output .navbox-title,.mw-parser-output .navbox-abovebelow{padding:0.25em 1em;line-height:1.5em;text-align:center}.mw-parser-output .navbox-group{white-space:nowrap;text-align:right}.mw-parser-output .navbox,.mw-parser-output .navbox-subgroup{background-color:#fdfdfd}.mw-parser-output .navbox-list{line-height:1.5em;border-color:#fdfdfd}.mw-parser-output .navbox-list-with-group{text-align:left;border-left-width:2px;border-left-style:solid}.mw-parser-output tr+tr>.navbox-abovebelow,.mw-parser-output tr+tr>.navbox-group,.mw-parser-output tr+tr>.navbox-image,.mw-parser-output tr+tr>.navbox-list{border-top:2px solid #fdfdfd}.mw-parser-output .navbox-title{background-color:#ccf}.mw-parser-output .navbox-abovebelow,.mw-parser-output .navbox-group,.mw-parser-output .navbox-subgroup .navbox-title{background-color:#ddf}.mw-parser-output .navbox-subgroup .navbox-group,.mw-parser-output .navbox-subgroup .navbox-abovebelow{background-color:#e6e6ff}.mw-parser-output .navbox-even{background-color:#f7f7f7}.mw-parser-output .navbox-odd{background-color:transparent}.mw-parser-output .navbox .hlist td dl,.mw-parser-output .navbox .hlist td ol,.mw-parser-output .navbox .hlist td ul,.mw-parser-output .navbox td.hlist dl,.mw-parser-output .navbox td.hlist ol,.mw-parser-output .navbox td.hlist ul{padding:0.125em 0}.mw-parser-output .navbox .navbar{display:block;font-size:100%}.mw-parser-output .navbox-title .navbar{float:left;text-align:left;margin-right:0.5em}body.skin--responsive .mw-parser-output .navbox-image img{max-width:none!important}@media print{body.ns-0 .mw-parser-output .navbox{display:none!important}}</style></div><div role="navigation" class="navbox" aria-labelledby="Photography477" style="padding:3px"><table class="nowraplinks mw-collapsible mw-collapsed navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Photography" title="Template:Photography"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Photography" title="Template talk:Photography"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Photography" title="Special:EditPage/Template:Photography"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Photography477" style="font-size:114%;margin:0 4em"><a href="/wiki/Photography" title="Photography">Photography</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Equipment</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Camera" title="Camera">Camera</a> <ul><li><a href="/wiki/Light_field_camera" title="Light field camera">light-field</a></li> <li><a href="/wiki/Digital_camera" title="Digital camera">digital</a></li> <li><a href="/wiki/Field_camera" title="Field camera">field</a></li> <li><a href="/wiki/Instant_camera" title="Instant camera">instant</a></li> <li><a href="/wiki/Camera_phone" title="Camera phone">phone</a></li> <li><a href="/wiki/Pinhole_camera" title="Pinhole camera">pinhole</a></li> <li><a href="/wiki/Press_camera" title="Press camera">press</a></li> <li><a href="/wiki/Rangefinder_camera" title="Rangefinder camera">rangefinder</a></li> <li><a href="/wiki/Single-lens_reflex_camera" title="Single-lens reflex camera">SLR</a></li> <li><a href="/wiki/Camera" title="Camera">still</a></li> <li><a href="/wiki/Twin-lens_reflex_camera" title="Twin-lens reflex camera">TLR</a></li> <li><a href="/wiki/Toy_camera" title="Toy camera">toy</a></li> <li><a href="/wiki/View_camera" title="View camera">view</a></li></ul></li> <li><a href="/wiki/Darkroom" title="Darkroom">Darkroom</a> <ul><li><a href="/wiki/Enlarger" title="Enlarger">enlarger</a></li> <li><a href="/wiki/Safelight" title="Safelight">safelight</a></li></ul></li> <li><a href="/wiki/Photographic_film" title="Photographic film">Film</a> <ul><li><a href="/wiki/Film_base" title="Film base">base</a></li> <li><a href="/wiki/Film_format" title="Film format">format</a></li> <li><a href="/wiki/Film_holder" title="Film holder">holder</a></li> <li><a href="/wiki/Film_stock" title="Film stock">stock</a></li> <li><a href="/wiki/List_of_photographic_films" title="List of photographic films">available films</a></li> <li><a href="/wiki/List_of_discontinued_photographic_films" title="List of discontinued photographic films">discontinued films</a></li></ul></li> <li><a href="/wiki/Photographic_filter" title="Photographic filter">Filter</a></li> <li><a href="/wiki/Flash_(photography)" title="Flash (photography)">Flash</a> <ul><li><a href="/wiki/Beauty_dish" title="Beauty dish">beauty dish</a></li> <li><a href="/wiki/Cucoloris" title="Cucoloris">cucoloris</a></li> <li><a href="/wiki/Gobo_(lighting)" title="Gobo (lighting)">gobo</a></li> <li><a href="/wiki/Hot_shoe" title="Hot shoe">hot shoe</a></li> <li><a href="/wiki/Lens_hood" title="Lens hood">lens hood</a></li> <li><a href="/wiki/Monolight" title="Monolight">monolight</a></li> <li><a href="/wiki/Reflector_(photography)" title="Reflector (photography)">reflector</a></li> <li><a href="/wiki/Snoot" title="Snoot">snoot</a></li> <li><a href="/wiki/Softbox" title="Softbox">softbox</a></li></ul></li> <li><a href="/wiki/Camera_lens" title="Camera lens">Lens</a> <ul><li><a href="/wiki/Long-focus_lens" title="Long-focus lens">long-focus</a></li> <li><a href="/wiki/Prime_lens" title="Prime lens">prime</a></li> <li><a href="/wiki/Zoom_lens" title="Zoom lens">zoom</a></li> <li><a href="/wiki/Wide-angle_lens" title="Wide-angle lens">wide-angle</a></li> <li><a href="/wiki/Fisheye_lens" title="Fisheye lens">fisheye</a></li> <li><a href="/wiki/Swivel_lens" title="Swivel lens">swivel</a></li> <li><a href="/wiki/Telephoto_lens" title="Telephoto lens">telephoto</a></li></ul></li> <li><a href="/wiki/List_of_photographic_equipment_makers" title="List of photographic equipment makers">Manufacturers</a></li> <li><a href="/wiki/Monopod" title="Monopod">Monopod</a></li> <li><a href="/wiki/Movie_projector" title="Movie projector">Movie projector</a></li> <li><a href="/wiki/Slide_projector" title="Slide projector">Slide projector</a></li> <li><a href="/wiki/Tripod_(photography)" title="Tripod (photography)">Tripod</a> <ul><li><a href="/wiki/Tripod_head" title="Tripod head">head</a></li></ul></li> <li><a href="/wiki/Zone_plate" title="Zone plate">Zone plate</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Terminology</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/35_mm_equivalent_focal_length" title="35 mm equivalent focal length">35 mm equivalent focal length</a></li> <li><a href="/wiki/Angle_of_view_(photography)" title="Angle of view (photography)">Angle of view</a></li> <li><a href="/wiki/Aperture" title="Aperture">Aperture</a></li> <li><a href="/wiki/Backscatter_(photography)" title="Backscatter (photography)">Backscatter</a></li> <li><a href="/wiki/Black-and-white" title="Black-and-white">Black-and-white</a></li> <li><a href="/wiki/Chromatic_aberration" title="Chromatic aberration">Chromatic aberration</a></li> <li><a href="/wiki/Circle_of_confusion" title="Circle of confusion">Circle of confusion</a></li> <li><a href="/wiki/Clipping_(photography)" title="Clipping (photography)">Clipping</a></li> <li><a href="/wiki/Color_balance" title="Color balance">Color balance</a></li> <li><a href="/wiki/Color_temperature" title="Color temperature">Color temperature</a></li> <li><a href="/wiki/Depth_of_field" title="Depth of field">Depth of field</a></li> <li><a href="/wiki/Depth_of_focus" title="Depth of focus">Depth of focus</a></li> <li><a href="/wiki/Exposure_(photography)" title="Exposure (photography)">Exposure</a></li> <li><a href="/wiki/Exposure_compensation" title="Exposure compensation">Exposure compensation</a></li> <li><a href="/wiki/Exposure_value" title="Exposure value">Exposure value</a></li> <li><a href="/wiki/Zebra_patterning" title="Zebra patterning">Zebra patterning</a></li> <li><a href="/wiki/F-number" title="F-number">F-number</a></li> <li><a href="/wiki/Film_format" title="Film format">Film format</a> <ul><li><a href="/wiki/Large_format" title="Large format">large</a></li> <li><a href="/wiki/Medium_format" title="Medium format">medium</a></li></ul></li> <li><a href="/wiki/Film_speed" title="Film speed">Film speed</a></li> <li><a class="mw-selflink selflink">Focal length</a></li> <li><a href="/wiki/Guide_number" title="Guide number">Guide number</a></li> <li><a href="/wiki/Hyperfocal_distance" title="Hyperfocal distance">Hyperfocal distance</a></li> <li><a href="/wiki/Lens_flare" title="Lens flare">Lens flare</a></li> <li><a href="/wiki/Metering_mode" title="Metering mode">Metering mode</a></li> <li><a href="/wiki/Perspective_distortion" title="Perspective distortion">Perspective distortion</a></li> <li><a href="/wiki/Photograph" title="Photograph">Photograph</a></li> <li><a href="/wiki/Photographic_printing" title="Photographic printing">Photographic printing</a> <ul><li><a href="/wiki/Albumen_print" title="Albumen print">Albumen</a></li></ul></li> <li><a href="/wiki/List_of_photographic_processes" title="List of photographic processes">Photographic processes</a></li> <li><a href="/wiki/Reciprocity_(photography)" title="Reciprocity (photography)">Reciprocity</a></li> <li><a href="/wiki/Red-eye_effect" title="Red-eye effect">Red-eye effect</a></li> <li><a href="/wiki/Science_of_photography" title="Science of photography">Science of photography</a></li> <li><a href="/wiki/Shutter_speed" title="Shutter speed">Shutter speed</a></li> <li><a href="/wiki/Flash_synchronization" title="Flash synchronization">Sync</a></li> <li><a href="/wiki/Zone_System" title="Zone System">Zone System</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Genres</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Abstract_photography" title="Abstract photography">Abstract</a></li> <li><a href="/wiki/Aerial_photography" title="Aerial photography">Aerial</a></li> <li><a href="/wiki/Aircraft_spotting" title="Aircraft spotting">Aircraft</a></li> <li><a href="/wiki/Architectural_photography" title="Architectural photography">Architectural</a></li> <li><a href="/wiki/Astrophotography" title="Astrophotography">Astrophotography</a></li> <li><a href="/wiki/Banquet_photography" title="Banquet photography">Banquet</a></li> <li><a href="/wiki/Candid_photography" title="Candid photography">Candid</a></li> <li><a href="/wiki/Conceptual_photography" title="Conceptual photography">Conceptual</a></li> <li><a href="/wiki/Conservation_photography" title="Conservation photography">Conservation</a></li> <li><a href="/wiki/Cloudscape_photography" title="Cloudscape photography">Cloudscape</a></li> <li><a href="/wiki/Documentary_photography" title="Documentary photography">Documentary</a></li> <li><a href="/wiki/Eclipse_photography" title="Eclipse photography">Eclipse</a></li> <li><a href="/wiki/Visual_anthropology" title="Visual anthropology">Ethnographic</a></li> <li><a href="/wiki/Erotic_photography" title="Erotic photography">Erotic</a></li> <li><a href="/wiki/Fashion_photography" title="Fashion photography">Fashion</a></li> <li><a href="/wiki/Fine-art_photography" title="Fine-art photography">Fine-art</a></li> <li><a href="/wiki/Fire_photography" title="Fire photography">Fire</a></li> <li><a href="/wiki/Forensic_photography" title="Forensic photography">Forensic</a></li> <li><a href="/wiki/Glamour_photography" title="Glamour photography">Glamour</a></li> <li><a href="/wiki/High-speed_photography" title="High-speed photography">High-speed</a></li> <li><a href="/wiki/Landscape_photography" title="Landscape photography">Landscape</a></li> <li><a href="/wiki/Monochrome_photography" title="Monochrome photography">Monochrome</a></li> <li><a href="/wiki/Nature_photography" title="Nature photography">Nature</a></li> <li><a href="/wiki/Neues_Sehen" title="Neues Sehen">Neues Sehen</a></li> <li><a href="/wiki/Nude_photography" title="Nude photography">Nude</a></li> <li><a href="/wiki/Photojournalism" title="Photojournalism">Photojournalism</a></li> <li><a href="/wiki/Pictorialism" title="Pictorialism">Pictorialism</a></li> <li><a href="/wiki/Pornography" title="Pornography">Pornography</a></li> <li><a href="/wiki/Portrait_photography" title="Portrait photography">Portrait</a></li> <li><a href="/wiki/Post-mortem_photography" title="Post-mortem photography">Post-mortem</a></li> <li><a href="/wiki/Ruins_photography" title="Ruins photography">Ruins</a></li> <li><a href="/wiki/Selfie" title="Selfie">Selfie</a> <ul><li><a href="/wiki/Space_selfie" title="Space selfie">space selfie</a></li></ul></li> <li><a href="/wiki/Social_documentary_photography" title="Social documentary photography">Social documentary</a></li> <li><a href="/wiki/Sports_photography" title="Sports photography">Sports</a></li> <li><a href="/wiki/Still_life_photography" title="Still life photography">Still life</a></li> <li><a href="/wiki/Stock_photography" title="Stock photography">Stock</a></li> <li><a href="/wiki/Straight_photography" title="Straight photography">Straight photography</a></li> <li><a href="/wiki/Street_photography" title="Street photography">Street</a></li> <li><a href="/wiki/Toy_camera" title="Toy camera">Toy camera</a></li> <li><a href="/wiki/Underwater_photography" title="Underwater photography">Underwater</a></li> <li><a href="/wiki/Vernacular_photography" title="Vernacular photography">Vernacular</a></li> <li><a href="/wiki/Wedding_photography" title="Wedding photography">Wedding</a></li> <li><a href="/wiki/Wildlife_photography" title="Wildlife photography">Wildlife</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Techniques</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Afocal_photography" title="Afocal photography">Afocal</a></li> <li><a href="/wiki/Bokeh" title="Bokeh">Bokeh</a></li> <li><a href="/wiki/Brenizer_method" title="Brenizer method">Brenizer</a></li> <li><a href="/wiki/Burst_mode_(photography)" title="Burst mode (photography)">Burst mode</a></li> <li><a href="/wiki/Contre-jour" title="Contre-jour">Contre-jour</a></li> <li><a href="/wiki/Exposing_to_the_right" title="Exposing to the right">ETTR</a></li> <li><a href="/wiki/Fill_flash" title="Fill flash">Fill flash</a></li> <li><a href="/wiki/Fireworks_photography" title="Fireworks photography">Fireworks</a></li> <li><a href="/wiki/Hand-colouring_of_photographs" title="Hand-colouring of photographs">Hand-colouring</a></li> <li><a href="/wiki/Harris_shutter" title="Harris shutter">Harris shutter</a></li> <li><a href="/wiki/High-speed_photography" title="High-speed photography">High-speed</a></li> <li><a href="/wiki/Holography" title="Holography">Holography</a></li> <li><a href="/wiki/Infrared_photography" title="Infrared photography">Infrared</a></li> <li><a href="/wiki/Intentional_camera_movement" title="Intentional camera movement">Intentional camera movement</a></li> <li><a href="/wiki/Kirlian_photography" title="Kirlian photography">Kirlian</a></li> <li><a href="/wiki/Kite_aerial_photography" title="Kite aerial photography">Kite aerial</a></li> <li><a href="/wiki/Lo-fi_photography" title="Lo-fi photography">Lo-fi photography</a></li> <li><a href="/wiki/Long-exposure_photography" title="Long-exposure photography">Long-exposure</a></li> <li><a href="/wiki/Luminogram" title="Luminogram">Luminogram</a></li> <li><a href="/wiki/Macro_photography" title="Macro photography">Macro</a></li> <li><a href="/wiki/Mordan%C3%A7age" title="Mordançage">Mordançage</a></li> <li><a href="/wiki/Multiple_exposure" title="Multiple exposure">Multiple exposure</a></li> <li><a href="/wiki/Multi-exposure_HDR_capture" title="Multi-exposure HDR capture">Multi-exposure HDR capture</a></li> <li><a href="/wiki/Night_photography" title="Night photography">Night</a></li> <li><a href="/wiki/Panning_(camera)" title="Panning (camera)">Panning</a></li> <li><a href="/wiki/Panoramic_photography" title="Panoramic photography">Panoramic</a></li> <li><a href="/wiki/Photogram" title="Photogram">Photogram</a></li> <li><a href="/wiki/Photographic_print_toning" title="Photographic print toning">Print toning</a></li> <li><a href="/wiki/Pigeon_photography" title="Pigeon photography">Pigeon photography</a></li> <li><a href="/wiki/Redscale" title="Redscale">Redscale</a></li> <li><a href="/wiki/Rephotography" title="Rephotography">Rephotography</a></li> <li><a href="/wiki/Rollout_photography" title="Rollout photography">Rollout</a></li> <li><a href="/wiki/Scanography" title="Scanography">Scanography</a></li> <li><a href="/wiki/Schlieren_photography" title="Schlieren photography">Schlieren photography</a></li> <li><a href="/wiki/Sabattier_effect" title="Sabattier effect">Sabattier effect</a></li> <li><a href="/wiki/Slow_motion" title="Slow motion">Slow motion</a></li> <li><a href="/wiki/Stereoscopy" title="Stereoscopy">Stereoscopy</a></li> <li><a href="/wiki/Stopping_down" title="Stopping down">Stopping down</a></li> <li><a href="/wiki/Strip_photography" title="Strip photography">Strip</a> <ul><li><a href="/wiki/Slit-scan_photography" title="Slit-scan photography">Slit-scan</a></li></ul></li> <li><a href="/wiki/Sun_printing" title="Sun printing">Sun printing</a></li> <li><a href="/wiki/Tilt%E2%80%93shift_photography" title="Tilt–shift photography">Tilt–shift</a> <ul><li><a href="/wiki/Miniature_faking" title="Miniature faking">Miniature faking</a></li></ul></li> <li><a href="/wiki/Time-lapse_photography" title="Time-lapse photography">Time-lapse</a></li> <li><a href="/wiki/Ultraviolet_photography" title="Ultraviolet photography">Ultraviolet</a></li> <li><a href="/wiki/Vignetting" title="Vignetting">Vignetting</a></li> <li><a href="/wiki/Xerox_art" title="Xerox art">Xerography</a></li> <li><a href="/wiki/Zoom_burst" title="Zoom burst">Zoom burst</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Composition_(visual_arts)" title="Composition (visual arts)">Composition</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Diagonal_method" title="Diagonal method">Diagonal method</a></li> <li><a href="/wiki/Framing_(visual_arts)" title="Framing (visual arts)">Framing</a></li> <li><a href="/wiki/Headroom_(photographic_framing)" title="Headroom (photographic framing)">Headroom</a></li> <li><a href="/wiki/Lead_room" title="Lead room">Lead room</a></li> <li><a href="/wiki/Rule_of_thirds" title="Rule of thirds">Rule of thirds</a></li> <li><a href="/wiki/Simplicity_(photography)" title="Simplicity (photography)">Simplicity</a></li> <li><a href="/wiki/Golden_triangle_(composition)" title="Golden triangle (composition)">Golden triangle (composition)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/History_of_photography" title="History of photography">History</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Timeline_of_photography_technology" title="Timeline of photography technology">Timeline of photography technology</a></li> <li><a href="/wiki/Ambrotype" title="Ambrotype">Ambrotype</a></li> <li><a href="/wiki/Film_photography" class="mw-redirect" title="Film photography">Film photography</a></li> <li><a href="/wiki/Autochrome_Lumi%C3%A8re" title="Autochrome Lumière">Autochrome Lumière</a></li> <li><a href="/wiki/Box_camera" title="Box camera">Box camera</a></li> <li><a href="/wiki/Calotype" title="Calotype">Calotype</a></li> <li><a href="/wiki/Camera_obscura" title="Camera obscura">Camera obscura</a></li> <li><a href="/wiki/Daguerreotype" title="Daguerreotype">Daguerreotype</a></li> <li><a href="/wiki/Dufaycolor" title="Dufaycolor">Dufaycolor</a></li> <li><a href="/wiki/Heliography" title="Heliography">Heliography</a></li> <li><a href="/wiki/Lippmann_plate" title="Lippmann plate">Lippmann plate</a></li> <li><a href="/wiki/Painted_photography_backdrops" title="Painted photography backdrops">Painted photography backdrops</a></li> <li><a href="/wiki/Photography_and_the_law" title="Photography and the law">Photography and the law</a></li> <li><a href="/wiki/Photographic_plate" title="Photographic plate">Glass plate</a></li> <li><a href="/wiki/Tintype" title="Tintype">Tintype</a></li> <li><a href="/wiki/Visual_arts" title="Visual arts">Visual arts</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Regional</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Photography_in_Albania" title="Photography in Albania">Albania</a></li> <li><a href="/wiki/Photography_in_Bangladesh" title="Photography in Bangladesh">Bangladesh</a></li> <li><a href="/wiki/Photography_in_Canada" title="Photography in Canada">Canada</a></li> <li><a href="/wiki/Photography_in_China" title="Photography in China">China</a></li> <li><a href="/wiki/Photography_in_Denmark" title="Photography in Denmark">Denmark</a></li> <li><a href="/wiki/Photography_in_Greece" title="Photography in Greece">Greece</a></li> <li><a href="/wiki/Photography_in_India" title="Photography in India">India</a></li> <li><a href="/wiki/Photography_in_Japan" title="Photography in Japan">Japan</a></li> <li><a href="/wiki/Photography_in_Korea" title="Photography in Korea">Korea</a></li> <li><a href="/wiki/Photography_in_Luxembourg" title="Photography in Luxembourg">Luxembourg</a></li> <li><a href="/wiki/Photography_in_Norway" title="Photography in Norway">Norway</a></li> <li><a href="/wiki/Photography_in_the_Philippines" title="Photography in the Philippines">Philippines</a></li> <li><a href="/wiki/Photography_in_Serbia" title="Photography in Serbia">Serbia</a></li> <li><a href="/wiki/Photography_in_Slovenia" class="mw-redirect" title="Photography in Slovenia">Slovenia</a></li> <li><a href="/wiki/Photography_in_Sudan" title="Photography in Sudan">Sudan</a></li> <li><a href="/wiki/Photography_in_Taiwan" title="Photography in Taiwan">Taiwan</a></li> <li><a href="/wiki/Photography_in_Turkey" title="Photography in Turkey">Turkey</a></li> <li><a href="/wiki/Photography_in_Ukraine" title="Photography in Ukraine">Ukraine</a></li> <li><a href="/wiki/Photography_in_the_United_States" title="Photography in the United States">United States</a></li> <li><a href="/wiki/Photography_in_Uzbekistan" title="Photography in Uzbekistan">Uzbekistan</a></li> <li><a href="/wiki/Photography_in_Vietnam" title="Photography in Vietnam">Vietnam</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Digital_photography" title="Digital photography">Digital photography</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Digital_camera" title="Digital camera">Digital camera</a> <ul><li><a href="/wiki/Digital_single-lens_reflex_camera" title="Digital single-lens reflex camera">D-SLR</a> <ul><li><a href="/wiki/Comparison_of_digital_SLRs" title="Comparison of digital SLRs">comparison</a></li></ul></li> <li><a href="/wiki/Mirrorless_camera" title="Mirrorless camera">MILC</a></li> <li><a href="/wiki/Digital_camera_back" title="Digital camera back">camera back</a></li></ul></li> <li><a href="/wiki/Digiscoping" title="Digiscoping">Digiscoping</a></li> <li><a href="/wiki/Comparison_of_digital_and_film_photography" title="Comparison of digital and film photography">Comparison of digital and film photography</a></li> <li><a href="/wiki/Film_scanner" title="Film scanner">Film scanner</a></li> <li><a href="/wiki/Image_sensor" title="Image sensor">Image sensor</a> <ul><li><a href="/wiki/Active-pixel_sensor" title="Active-pixel sensor">CMOS APS</a></li> <li><a href="/wiki/Charge-coupled_device" title="Charge-coupled device">CCD</a></li> <li><a href="/wiki/Three-CCD_camera" title="Three-CCD camera">Three-CCD camera</a></li> <li><a href="/wiki/Foveon_X3_sensor" title="Foveon X3 sensor">Foveon X3 sensor</a></li></ul></li> <li><a href="/wiki/Image_sharing" title="Image sharing">Image sharing</a></li> <li><a href="/wiki/Pixel" title="Pixel">Pixel</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Color_photography" title="Color photography">Color photography</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Color_print_film" title="Color print film">Print film</a> <ul><li><a href="/wiki/Chromogenic_print" title="Chromogenic print">Chromogenic print</a></li></ul></li> <li><a href="/wiki/Reversal_film" title="Reversal film">Reversal film</a></li> <li><a href="/wiki/Color_management" title="Color management">Color management</a> <ul><li><a href="/wiki/Color_space" title="Color space">color space</a></li> <li><a href="/wiki/Primary_color" title="Primary color">primary color</a></li> <li><a href="/wiki/CMYK_color_model" title="CMYK color model">CMYK color model</a></li> <li><a href="/wiki/RGB_color_model" title="RGB color model">RGB color model</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Photographic_processing" title="Photographic processing">Photographic<br />processing</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Bleach_bypass" title="Bleach bypass">Bleach bypass</a></li> <li><a href="/wiki/C-41_process" title="C-41 process">C-41 process</a></li> <li><a href="/wiki/Collodion_process" title="Collodion process">Collodion process</a></li> <li><a href="/wiki/Cross_processing" title="Cross processing">Cross processing</a></li> <li><a href="/wiki/Cyanotype" title="Cyanotype">Cyanotype</a></li> <li><a href="/wiki/Photographic_developer" title="Photographic developer">Developer</a></li> <li><a href="/wiki/Digital_image_processing" title="Digital image processing">Digital image processing</a></li> <li><a href="/wiki/Dye_coupler" title="Dye coupler">Dye coupler</a></li> <li><a href="/wiki/E-6_process" title="E-6 process">E-6 process</a></li> <li><a href="/wiki/Photographic_fixer" title="Photographic fixer">Fixer</a></li> <li><a href="/wiki/Gelatin_silver_process" class="mw-redirect" title="Gelatin silver process">Gelatin silver process</a></li> <li><a href="/wiki/Gum_printing" title="Gum printing">Gum printing</a></li> <li><a href="/wiki/Instant_film" title="Instant film">Instant film</a></li> <li><a href="/wiki/K-14_process" title="K-14 process">K-14 process</a></li> <li><a href="/wiki/Print_permanence" title="Print permanence">Print permanence</a></li> <li><a href="/wiki/Push_processing" title="Push processing">Push processing</a></li> <li><a href="/wiki/Stop_bath" title="Stop bath">Stop bath</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Lists</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/List_of_largest_photographs" title="List of largest photographs">Largest photographs</a></li> <li><a href="/wiki/List_of_most_expensive_photographs" title="List of most expensive photographs">Most expensive photographs</a></li> <li><a href="/wiki/List_of_museums_devoted_to_one_photographer" title="List of museums devoted to one photographer">Museums devoted to one photographer</a></li> <li><a href="/wiki/List_of_photographs_considered_the_most_important" title="List of photographs considered the most important">Photographs considered the most important</a></li> <li><a href="/wiki/List_of_photographers" title="List of photographers">Photographers</a> <ul><li><a href="/wiki/List_of_Norwegian_photographers" title="List of Norwegian photographers">Norwegian</a></li> <li><a href="/wiki/List_of_Polish_photographers" title="List of Polish photographers">Polish</a></li> <li><a href="/wiki/List_of_street_photographers" title="List of street photographers">street</a></li> <li><a href="/wiki/List_of_women_photographers" title="List of women photographers">women</a></li></ul></li> <li><a href="/wiki/List_of_photography_periodicals" title="List of photography periodicals">Photography periodicals</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Conservation_and_restoration_of_photographs" title="Conservation and restoration of photographs">Conservation and restoration of photographs</a> <ul><li><a href="/wiki/Conservation_and_restoration_of_film" title="Conservation and restoration of film">film</a></li> <li><a href="/wiki/Conservation_and_restoration_of_photographic_plates" title="Conservation and restoration of photographic plates">photographic plates</a></li></ul></li> <li><a href="/wiki/Toy_camera#Lomography" title="Toy camera">Lomography</a></li> <li><a href="/wiki/Polaroid_art" title="Polaroid art">Polaroid art</a></li> <li><a href="/wiki/Stereoscopy" title="Stereoscopy">Stereoscopy</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow hlist" colspan="2"><div> <ul><li><span class="noviewer" typeof="mw:File"><span title="Category"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/31px-Symbol_category_class.svg.png 2x" data-file-width="180" data-file-height="185" /></span></span> <a href="/wiki/Category:Photography" title="Category:Photography">Category</a></li> <li><span class="noviewer" typeof="mw:File"><span title="Outline"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/4/41/Global_thinking.svg/20px-Global_thinking.svg.png" decoding="async" width="10" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/41/Global_thinking.svg/40px-Global_thinking.svg.png 2x" data-file-width="130" data-file-height="200" /></span></span> <a href="/wiki/Outline_of_photography" title="Outline of photography">Outline</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235" /></div><div role="navigation" class="navbox authority-control" aria-label="Navbox390" style="padding:3px"><table class="nowraplinks hlist navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Help:Authority_control" title="Help:Authority control">Authority control databases</a>: National <span class="mw-valign-text-top noprint" typeof="mw:File/Frameless"><a href="https://www.wikidata.org/wiki/Q193540#identifiers" title="Edit this at Wikidata"><img alt="Edit this at Wikidata" src="//upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/10px-OOjs_UI_icon_edit-ltr-progressive.svg.png" decoding="async" width="10" height="10" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/15px-OOjs_UI_icon_edit-ltr-progressive.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/20px-OOjs_UI_icon_edit-ltr-progressive.svg.png 2x" data-file-width="20" data-file-height="20" /></a></span></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"><ul><li><span class="uid"><a rel="nofollow" class="external text" href="https://d-nb.info/gnd/4344267-5">Germany</a></span></li></ul></div></td></tr></tbody></table></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?useformat=desktop&type=1x1&usesul3=0" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Focal_length&oldid=1280478286">https://en.wikipedia.org/w/index.php?title=Focal_length&oldid=1280478286</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/wiki/Category:Geometrical_optics" title="Category:Geometrical optics">Geometrical optics</a></li><li><a href="/wiki/Category:Length" title="Category:Length">Length</a></li><li><a href="/wiki/Category:Science_of_photography" title="Category:Science of photography">Science of photography</a></li><li><a href="/wiki/Category:Optical_quantities" title="Category:Optical quantities">Optical quantities</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_matches_Wikidata" title="Category:Short description matches Wikidata">Short description matches Wikidata</a></li><li><a href="/wiki/Category:Articles_needing_additional_references_from_November_2021" title="Category:Articles needing additional references from November 2021">Articles needing additional references from November 2021</a></li><li><a href="/wiki/Category:All_articles_needing_additional_references" title="Category:All articles needing additional references">All articles needing additional references</a></li><li><a href="/wiki/Category:Commons_category_link_is_on_Wikidata" title="Category:Commons category link is on Wikidata">Commons category link is on Wikidata</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 14 March 2025, at 20:48<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. By using this site, you agree to the <a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Terms_of_Use" class="extiw" title="foundation:Special:MyLanguage/Policy:Terms of Use">Terms of Use</a> and <a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Privacy_policy" class="extiw" title="foundation:Special:MyLanguage/Policy:Privacy policy">Privacy Policy</a>. Wikipedia® is a registered trademark of the <a rel="nofollow" class="external text" href="https://wikimediafoundation.org/">Wikimedia Foundation, Inc.</a>, a non-profit organization.</li> </ul> <ul id="footer-places"> <li id="footer-places-privacy"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Privacy_policy">Privacy policy</a></li> <li id="footer-places-about"><a href="/wiki/Wikipedia:About">About Wikipedia</a></li> <li id="footer-places-disclaimers"><a href="/wiki/Wikipedia:General_disclaimer">Disclaimers</a></li> <li id="footer-places-contact"><a href="//en.wikipedia.org/wiki/Wikipedia:Contact_us">Contact Wikipedia</a></li> <li id="footer-places-wm-codeofconduct"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Universal_Code_of_Conduct">Code of Conduct</a></li> <li id="footer-places-developers"><a href="https://developer.wikimedia.org">Developers</a></li> <li id="footer-places-statslink"><a href="https://stats.wikimedia.org/#/en.wikipedia.org">Statistics</a></li> <li id="footer-places-cookiestatement"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Cookie_statement">Cookie statement</a></li> <li id="footer-places-mobileview"><a href="//en.m.wikipedia.org/w/index.php?title=Focal_length&mobileaction=toggle_view_mobile" class="noprint stopMobileRedirectToggle">Mobile view</a></li> </ul> <ul id="footer-icons" class="noprint"> <li id="footer-copyrightico"><a href="https://www.wikimedia.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><picture><source media="(min-width: 500px)" srcset="/static/images/footer/wikimedia-button.svg" width="84" height="29"><img src="/static/images/footer/wikimedia.svg" width="25" height="25" alt="Wikimedia Foundation" lang="en" loading="lazy"></picture></a></li> <li id="footer-poweredbyico"><a href="https://www.mediawiki.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><picture><source media="(min-width: 500px)" srcset="/w/resources/assets/poweredby_mediawiki.svg" width="88" height="31"><img src="/w/resources/assets/mediawiki_compact.svg" alt="Powered by MediaWiki" lang="en" width="25" height="25" loading="lazy"></picture></a></li> </ul> </footer> </div> </div> </div> <div class="vector-header-container vector-sticky-header-container"> <div id="vector-sticky-header" class="vector-sticky-header"> <div class="vector-sticky-header-start"> <div class="vector-sticky-header-icon-start vector-button-flush-left vector-button-flush-right" aria-hidden="true"> <button class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-sticky-header-search-toggle" tabindex="-1" data-event-name="ui.vector-sticky-search-form.icon"><span class="vector-icon mw-ui-icon-search mw-ui-icon-wikimedia-search"></span> <span>Search</span> </button> </div> <div role="search" class="vector-search-box-vue vector-search-box-show-thumbnail vector-search-box"> <div class="vector-typeahead-search-container"> <div class="cdx-typeahead-search cdx-typeahead-search--show-thumbnail"> <form action="/w/index.php" id="vector-sticky-search-form" class="cdx-search-input cdx-search-input--has-end-button"> <div class="cdx-search-input__input-wrapper" data-search-loc="header-moved"> <div class="cdx-text-input cdx-text-input--has-start-icon"> <input class="cdx-text-input__input" type="search" name="search" placeholder="Search Wikipedia"> <span class="cdx-text-input__icon cdx-text-input__start-icon"></span> </div> <input type="hidden" name="title" value="Special:Search"> </div> <button class="cdx-button cdx-search-input__end-button">Search</button> </form> </div> </div> </div> <div class="vector-sticky-header-context-bar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-sticky-header-toc" class="vector-dropdown mw-portlet mw-portlet-sticky-header-toc vector-sticky-header-toc vector-button-flush-left" > <input type="checkbox" id="vector-sticky-header-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-sticky-header-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-sticky-header-toc-label" for="vector-sticky-header-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-sticky-header-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <div class="vector-sticky-header-context-bar-primary" aria-hidden="true" ><span class="mw-page-title-main">Focal length</span></div> </div> </div> <div class="vector-sticky-header-end" aria-hidden="true"> <div class="vector-sticky-header-icons"> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-talk-sticky-header" tabindex="-1" data-event-name="talk-sticky-header"><span class="vector-icon mw-ui-icon-speechBubbles mw-ui-icon-wikimedia-speechBubbles"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-subject-sticky-header" tabindex="-1" data-event-name="subject-sticky-header"><span class="vector-icon mw-ui-icon-article mw-ui-icon-wikimedia-article"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-history-sticky-header" tabindex="-1" data-event-name="history-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-history mw-ui-icon-wikimedia-wikimedia-history"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only mw-watchlink" id="ca-watchstar-sticky-header" tabindex="-1" data-event-name="watch-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-star mw-ui-icon-wikimedia-wikimedia-star"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-edit-sticky-header" tabindex="-1" data-event-name="wikitext-edit-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-wikiText mw-ui-icon-wikimedia-wikimedia-wikiText"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-ve-edit-sticky-header" tabindex="-1" data-event-name="ve-edit-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-edit mw-ui-icon-wikimedia-wikimedia-edit"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-viewsource-sticky-header" tabindex="-1" data-event-name="ve-edit-protected-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-editLock mw-ui-icon-wikimedia-wikimedia-editLock"></span> <span></span> </a> </div> <div class="vector-sticky-header-buttons"> <button class="cdx-button cdx-button--weight-quiet mw-interlanguage-selector" id="p-lang-btn-sticky-header" tabindex="-1" data-event-name="ui.dropdown-p-lang-btn-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-language mw-ui-icon-wikimedia-wikimedia-language"></span> <span>55 languages</span> </button> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive" id="ca-addsection-sticky-header" tabindex="-1" data-event-name="addsection-sticky-header"><span class="vector-icon mw-ui-icon-speechBubbleAdd-progressive mw-ui-icon-wikimedia-speechBubbleAdd-progressive"></span> <span>Add topic</span> </a> </div> <div class="vector-sticky-header-icon-end"> <div class="vector-user-links"> </div> </div> </div> </div> </div> <div class="mw-portlet mw-portlet-dock-bottom emptyPortlet" id="p-dock-bottom"> <ul> </ul> </div> <script>(RLQ=window.RLQ||[]).push(function(){mw.config.set({"wgHostname":"mw-web.eqiad.main-d6f4c4464-sfzgf","wgBackendResponseTime":156,"wgPageParseReport":{"limitreport":{"cputime":"0.514","walltime":"0.803","ppvisitednodes":{"value":3576,"limit":1000000},"postexpandincludesize":{"value":80698,"limit":2097152},"templateargumentsize":{"value":4231,"limit":2097152},"expansiondepth":{"value":13,"limit":100},"expensivefunctioncount":{"value":4,"limit":500},"unstrip-depth":{"value":1,"limit":20},"unstrip-size":{"value":57879,"limit":5000000},"entityaccesscount":{"value":1,"limit":400},"timingprofile":["100.00% 640.253 1 -total"," 18.69% 119.656 1 Template:Reflist"," 16.30% 104.370 1 Template:Photography_subject"," 15.16% 97.093 1 Template:Navbox"," 14.65% 93.802 8 Template:Cite_book"," 13.82% 88.465 1 Template:More_citations"," 12.83% 82.137 1 Template:Ambox"," 12.12% 77.628 1 Template:Short_description"," 9.59% 61.379 1 Template:Redirect"," 6.71% 42.976 2 Template:Pagetype"]},"scribunto":{"limitreport-timeusage":{"value":"0.300","limit":"10.000"},"limitreport-memusage":{"value":7626107,"limit":52428800}},"cachereport":{"origin":"mw-web.eqiad.main-65bf7dbd64-c5hkp","timestamp":"20250325193202","ttl":2592000,"transientcontent":false}}});});</script> <script type="application/ld+json">{"@context":"https:\/\/schema.org","@type":"Article","name":"Focal length","url":"https:\/\/en.wikipedia.org\/wiki\/Focal_length","sameAs":"http:\/\/www.wikidata.org\/entity\/Q193540","mainEntity":"http:\/\/www.wikidata.org\/entity\/Q193540","author":{"@type":"Organization","name":"Contributors to Wikimedia projects"},"publisher":{"@type":"Organization","name":"Wikimedia Foundation, Inc.","logo":{"@type":"ImageObject","url":"https:\/\/www.wikimedia.org\/static\/images\/wmf-hor-googpub.png"}},"datePublished":"2002-09-08T12:03:31Z","dateModified":"2025-03-14T20:48:02Z","headline":"measure of how strongly an optical system converges or diverges light"}</script> </body> </html>