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<h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Diaphragm (optics)</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. 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mw-list-item"><a href="https://az.wikipedia.org/wiki/Diafraqma_(foto)" title="Diafraqma (foto) – Azerbaijani" lang="az" hreflang="az" data-title="Diafraqma (foto)" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target"><span>Azərbaycanca</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%91%D0%BB%D0%B5%D0%BD%D0%B4%D0%B0" title="Бленда – Bulgarian" lang="bg" hreflang="bg" data-title="Бленда" 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/Blendn_(Photographie)" title="Blendn (Photographie) – Bavarian" lang="bar" hreflang="bar" data-title="Blendn (Photographie)" 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/Diafragma_(%C3%B2ptica)" title="Diafragma (òptica) – Catalan" lang="ca" hreflang="ca" data-title="Diafragma (òptica)" 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/Clona" title="Clona – Czech" lang="cs" hreflang="cs" data-title="Clona" 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/Bl%C3%A6nde" title="Blænde – Danish" lang="da" hreflang="da" data-title="Blænde" 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/Fotografische_Blende" title="Fotografische Blende – German" lang="de" hreflang="de" data-title="Fotografische Blende" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Diafragma_(%C3%B3ptica)" title="Diafragma (óptica) – Spanish" lang="es" hreflang="es" data-title="Diafragma (óptica)" 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/Diafragmo_(fotado)" title="Diafragmo (fotado) – Esperanto" lang="eo" hreflang="eo" data-title="Diafragmo (fotado)" 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/Diafragma_(optika)" title="Diafragma (optika) – Basque" lang="eu" hreflang="eu" data-title="Diafragma (optika)" 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/%D8%AF%DB%8C%D8%A7%D9%81%D8%B1%D8%A7%DA%AF%D9%85" title="دیافراگم – Persian" lang="fa" hreflang="fa" data-title="دیافراگم" 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/Diaphragme_(optique)" title="Diaphragme (optique) – French" lang="fr" hreflang="fr" data-title="Diaphragme (optique)" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ga mw-list-item"><a href="https://ga.wikipedia.org/wiki/Spiara" title="Spiara – Irish" lang="ga" hreflang="ga" data-title="Spiara" data-language-autonym="Gaeilge" data-language-local-name="Irish" class="interlanguage-link-target"><span>Gaeilge</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Diafragma_(fotografi)" title="Diafragma (fotografi) – Indonesian" lang="id" hreflang="id" data-title="Diafragma (fotografi)" 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-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Diaframma_(ottica)" title="Diaframma (ottica) – Italian" lang="it" hreflang="it" data-title="Diaframma (ottica)" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%A6%D7%9E%D7%A6%D7%9D" title="צמצם – Hebrew" lang="he" hreflang="he" data-title="צמצם" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-ky mw-list-item"><a href="https://ky.wikipedia.org/wiki/%D0%94%D0%B8%D0%B0%D1%84%D1%80%D0%B0%D0%B3%D0%BC%D0%B0_(%D0%BE%D0%BF%D1%82%D0%B8%D0%BA%D0%B0%D0%B4%D0%B0)" title="Диафрагма (оптикада) – Kyrgyz" lang="ky" hreflang="ky" data-title="Диафрагма (оптикада)" data-language-autonym="Кыргызча" data-language-local-name="Kyrgyz" class="interlanguage-link-target"><span>Кыргызча</span></a></li><li class="interlanguage-link interwiki-lb mw-list-item"><a href="https://lb.wikipedia.org/wiki/Blend_(Fotoapparat)" title="Blend (Fotoapparat) – Luxembourgish" lang="lb" hreflang="lb" data-title="Blend (Fotoapparat)" 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/Diafragma_(fotografija)" title="Diafragma (fotografija) – Lithuanian" lang="lt" hreflang="lt" data-title="Diafragma (fotografija)" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-li mw-list-item"><a href="https://li.wikipedia.org/wiki/Diafragma" title="Diafragma – Limburgish" lang="li" hreflang="li" data-title="Diafragma" data-language-autonym="Limburgs" data-language-local-name="Limburgish" class="interlanguage-link-target"><span>Limburgs</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Diafragma_(optica)" title="Diafragma (optica) – Dutch" lang="nl" hreflang="nl" data-title="Diafragma (optica)" 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%B5%9E%E3%82%8A_(%E5%85%89%E5%AD%A6)" title="絞り (光学) – Japanese" lang="ja" hreflang="ja" data-title="絞り (光学)" 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/Irisblender" title="Irisblender – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Irisblender" 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/Irisblendar" title="Irisblendar – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Irisblendar" 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-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Przys%C5%82ona_fotograficzna" title="Przysłona fotograficzna – Polish" lang="pl" hreflang="pl" data-title="Przysłona fotograficzna" 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/Diafragma_fotogr%C3%A1fico" title="Diafragma fotográfico – Portuguese" lang="pt" hreflang="pt" data-title="Diafragma fotográfico" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%94%D0%B8%D0%B0%D1%84%D1%80%D0%B0%D0%B3%D0%BC%D0%B0_(%D0%BE%D0%BF%D1%82%D0%B8%D0%BA%D0%B0)" title="Диафрагма (оптика) – Russian" lang="ru" hreflang="ru" data-title="Диафрагма (оптика)" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-sq mw-list-item"><a href="https://sq.wikipedia.org/wiki/Diafragma_(optik)" title="Diafragma (optik) – Albanian" lang="sq" hreflang="sq" data-title="Diafragma (optik)" data-language-autonym="Shqip" data-language-local-name="Albanian" class="interlanguage-link-target"><span>Shqip</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Clona_(fotografia)" title="Clona (fotografia) – Slovak" lang="sk" hreflang="sk" data-title="Clona (fotografia)" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Valotusaukko" title="Valotusaukko – Finnish" lang="fi" hreflang="fi" data-title="Valotusaukko" 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/Bl%C3%A4ndare" title="Bländare – Swedish" lang="sv" hreflang="sv" data-title="Bländare" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B9%81%E0%B8%9C%E0%B9%88%E0%B8%99%E0%B8%8A%E0%B9%88%E0%B8%AD%E0%B8%87%E0%B8%A3%E0%B8%B1%E0%B8%9A%E0%B9%81%E0%B8%AA%E0%B8%87" title="แผ่นช่องรับแสง – Thai" lang="th" hreflang="th" data-title="แผ่นช่องรับแสง" 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/Diyafram_(optik)" title="Diyafram (optik) – Turkish" lang="tr" hreflang="tr" data-title="Diyafram (optik)" 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%94%D1%96%D0%B0%D1%84%D1%80%D0%B0%D0%B3%D0%BC%D0%B0_(%D1%84%D0%BE%D1%82%D0%BE%D0%B3%D1%80%D0%B0%D1%84%D1%96%D1%8F)" title="Діафрагма (фотографія) – Ukrainian" lang="uk" hreflang="uk" data-title="Діафрагма (фотографія)" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/Kh%E1%BA%A9u_%C4%91%E1%BB%99" title="Khẩu độ – Vietnamese" lang="vi" hreflang="vi" data-title="Khẩu độ" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</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/Q261732#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 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</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">Thin opaque structure with an opening (aperture) at its center</div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:RotatingDiaphragm_Derr1906.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/en/d/d4/RotatingDiaphragm_Derr1906.png" decoding="async" width="220" height="300" class="mw-file-element" data-file-width="220" data-file-height="300" /></a><figcaption>A <a href="/wiki/Carl_Zeiss_AG" title="Carl Zeiss AG">Zeiss</a> rotating diaphragm, 1906.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> One diaphragm with five <a href="/wiki/Aperture" title="Aperture">apertures</a>.</figcaption></figure> <p>In <a href="/wiki/Optics" title="Optics">optics</a>, a <b>diaphragm</b> is a thin opaque structure with an opening (<a href="/wiki/Aperture" title="Aperture">aperture</a>) at its center. The role of the diaphragm is to <i>stop</i> the passage of light, except for the light passing through the <i>aperture</i>. Thus it is also called a <b>stop</b> (an <a href="/wiki/Aperture_stop" class="mw-redirect" title="Aperture stop">aperture stop</a>, if it limits the brightness of light reaching the focal plane, or a <b>field stop</b> or <b>flare stop</b> for other uses of diaphragms in lenses). The diaphragm is placed in the light path of a <a href="/wiki/Lens_(optics)" class="mw-redirect" title="Lens (optics)">lens</a> or <a href="/wiki/Photographic_lens" class="mw-redirect" title="Photographic lens">objective</a>, and the size of the aperture regulates the amount of light that passes through the lens. The centre of the diaphragm's aperture coincides with the <a href="/wiki/Optical_axis" title="Optical axis">optical axis</a> of the lens system. </p><p>Most modern cameras use a type of adjustable diaphragm known as an <b>iris diaphragm</b>, and often referred to simply as an <b>iris</b>. </p><p>See the articles on <a href="/wiki/Aperture" title="Aperture">aperture</a> and <a href="/wiki/F-number" title="F-number">f-number</a> for the photographic effect and system of quantification of varying the opening in the diaphragm. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Iris_diaphragms_versus_other_types"><span class="anchor" id="Aperture_shape"></span><span class="anchor" id="Diffusion_disc"></span><span class="anchor" id="Sieve_aperture"></span><span class="anchor" id="Sector_aperture"></span>Iris diaphragms versus other types</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Diaphragm_(optics)&action=edit&section=1" title="Edit section: Iris diaphragms versus other types"><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:Iris_Diaphragm.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/48/Iris_Diaphragm.gif/220px-Iris_Diaphragm.gif" decoding="async" width="220" height="199" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/48/Iris_Diaphragm.gif/330px-Iris_Diaphragm.gif 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/48/Iris_Diaphragm.gif/440px-Iris_Diaphragm.gif 2x" data-file-width="672" data-file-height="607" /></a><figcaption>Nine-blade iris</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Prntacon-lens-diaphragm.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Prntacon-lens-diaphragm.jpg/220px-Prntacon-lens-diaphragm.jpg" decoding="async" width="220" height="220" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Prntacon-lens-diaphragm.jpg/330px-Prntacon-lens-diaphragm.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Prntacon-lens-diaphragm.jpg/440px-Prntacon-lens-diaphragm.jpg 2x" data-file-width="1676" data-file-height="1675" /></a><figcaption>Pentacon 2.8/135 lens with 15-blade iris</figcaption></figure> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Aperture_in_Canon_50mm_f1.8_II_lens.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/8a/Aperture_in_Canon_50mm_f1.8_II_lens.jpg/220px-Aperture_in_Canon_50mm_f1.8_II_lens.jpg" decoding="async" width="220" height="223" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/8a/Aperture_in_Canon_50mm_f1.8_II_lens.jpg/330px-Aperture_in_Canon_50mm_f1.8_II_lens.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/8a/Aperture_in_Canon_50mm_f1.8_II_lens.jpg/440px-Aperture_in_Canon_50mm_f1.8_II_lens.jpg 2x" data-file-width="1712" data-file-height="1736" /></a><figcaption>Aperture mechanism of Canon 50mm f/1.8 II lens, with five blades</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Human_eye_with_limbal_ring,_anterior_view.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/96/Human_eye_with_limbal_ring%2C_anterior_view.jpg/220px-Human_eye_with_limbal_ring%2C_anterior_view.jpg" decoding="async" width="220" height="124" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/96/Human_eye_with_limbal_ring%2C_anterior_view.jpg/330px-Human_eye_with_limbal_ring%2C_anterior_view.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/96/Human_eye_with_limbal_ring%2C_anterior_view.jpg/440px-Human_eye_with_limbal_ring%2C_anterior_view.jpg 2x" data-file-width="1200" data-file-height="675" /></a><figcaption>In the human eye, the iris (light brown) acts as the diaphragm and continuously constricts and dilates its aperture (the pupil)</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:750nm_laser_beam_passing_through_an_iris_diaphragm.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/82/750nm_laser_beam_passing_through_an_iris_diaphragm.gif/220px-750nm_laser_beam_passing_through_an_iris_diaphragm.gif" decoding="async" width="220" height="391" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/8/82/750nm_laser_beam_passing_through_an_iris_diaphragm.gif 1.5x" data-file-width="240" data-file-height="426" /></a><figcaption>A 750<a href="/wiki/Nanometer" class="mw-redirect" title="Nanometer">nm</a> <a href="/wiki/Titanium-sapphire_laser" title="Titanium-sapphire laser">titanium-sapphire laser</a> beam passing through an iris diaphragm, while opening and closing the iris. Note changes in beam diameter observed on the downstream golden mirror.</figcaption></figure> <p>A natural optical system that has a diaphragm and an aperture is the <a href="/wiki/Human_eye" title="Human eye">human eye</a>. The <a href="/wiki/Iris_(anatomy)" title="Iris (anatomy)">iris</a> is the diaphragm, the <a href="/wiki/Pupil" title="Pupil">pupil</a> is the aperture. In the human eye, the iris can both constrict and dilate, which varies the size of the pupil. Unsurprisingly, a <a href="/wiki/Photographic_lens" class="mw-redirect" title="Photographic lens">photographic lens</a> with the ability to continuously vary the size of its aperture (the hole in the middle of the annular structure) is known as an iris diaphragm. </p><p>An iris diaphragm can reduce the amount of light that hits a detector by decreasing the aperture, usually with "leaves" or "blades" that form a circle.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>In the early years of photography, a lens could be fitted with one of a set of interchangeable diaphragms,<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> often as brass strips known as <a href="/wiki/Waterhouse_stop" title="Waterhouse stop">Waterhouse stops</a> or Waterhouse diaphragms. The iris diaphragm in most modern still and video cameras is adjusted by movable blades, simulating the iris of the eye. </p><p>The diaphragm has two to twenty blades (with most lenses today featuring between five and ten blades), depending on price and quality of the device in which it is used. Straight blades result in <a href="/wiki/Polygon" title="Polygon">polygon</a> shape of the diaphragm opening, while curved blades improve the roundness of the iris opening. In a photograph, the number of blades that the iris diaphragm has can be guessed by counting the number of <a href="/wiki/Diffraction_spike" title="Diffraction spike">diffraction spikes</a> converging from a light source or bright reflection. For an odd number of blades, there are twice as many spikes as there are blades. </p><p>In case of an even number of blades, the two spikes per blade will overlap each other, so the number of spikes visible will be the number of blades in the diaphragm used. This is most apparent in pictures taken in the dark with small bright spots, for example night cityscapes. Some cameras, such as the <a href="/wiki/Olympus_XA" title="Olympus XA">Olympus XA</a> or lenses such as the MC Zenitar-ME1, however, use a two-bladed diaphragm with right-angle blades creating a square aperture. </p><p>Similarly, out-of-focus points of light (<a href="/wiki/Circle_of_confusion" title="Circle of confusion">circles of confusion</a>) appear as polygons with the same number of sides as the <a href="/wiki/Aperture" title="Aperture">aperture</a> has blades. If the blurred light is circular, then it can be inferred that the aperture is either round or the image was shot "wide-open" (with the blades recessed into the sides of the lens, allowing the interior edge of the lens barrel to effectively become the iris). </p><p>The shape of the iris opening has a direct relation with the appearance of the blurred out-of-focus areas in an image called <i><a href="/wiki/Bokeh" title="Bokeh">bokeh</a></i>. A rounder opening produces softer and more natural out-of-focus areas. </p><p>Some lenses utilize specially shaped diaphragms in order to create certain effects. This includes the <i>diffusion discs</i> or <i>sieve aperture</i> of the <a href="/wiki/Rodenstock_Imagon" title="Rodenstock Imagon">Rodenstock Tiefenbildner-Imagon</a>, Fuji and Sima <a href="/wiki/Soft_focus" title="Soft focus">soft focus</a> lenses, the <i>sector aperture</i> of <a href="/w/index.php?title=Seibold%27s_Dreamagon&action=edit&redlink=1" class="new" title="Seibold's Dreamagon (page does not exist)">Seibold's Dreamagon</a>, or the circular <a href="/wiki/Apodization_filter" class="mw-redirect" title="Apodization filter">apodization filter</a> in the <a href="/wiki/Minolta" title="Minolta">Minolta</a>/<a href="/wiki/Sony" title="Sony">Sony</a> <a href="/wiki/Smooth_Trans_Focus" title="Smooth Trans Focus">Smooth Trans Focus</a> or <a href="/wiki/Fujinon_XF_56mm_F1.2_R_APD_lens" class="mw-redirect" title="Fujinon XF 56mm F1.2 R APD lens">Fujifilm APD</a> lenses. </p><p>Some modern automatic <a href="/wiki/Point-and-shoot_camera" title="Point-and-shoot camera">point-and-shoot cameras</a> do not have a diaphragm at all, and simulate aperture changes by using an automatic <a href="/wiki/ND_filter" class="mw-redirect" title="ND filter">ND filter</a>. Unlike a real diaphragm, this has no effect on <a href="/wiki/Depth_of_field" title="Depth of field">depth of field</a>. A real diaphragm when more-closed will cause the depth of field to <i>increase</i> (i.e., cause the background and the subject to both appear more in-focus at the same time) and if the diaphragm is opened up again the depth of field will <i>decrease</i> (i.e., the background and foreground will share less and less of the same focal plane).<sup id="cite_ref-AscherPincus2007_4-0" class="reference"><a href="#cite_note-AscherPincus2007-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="History">History</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Diaphragm_(optics)&action=edit&section=2" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In his 1567 work <i>La Pratica della Perspettiva</i> Venetian nobleman <a href="/wiki/Daniele_Barbaro" title="Daniele Barbaro">Daniele Barbaro</a> (1514–1570) described using a camera obscura with a biconvex lens as a drawing aid and points out that the picture is more vivid if the lens is covered as much as to leave a circumference in the middle.<sup id="cite_ref-Ilardi_5-0" class="reference"><a href="#cite_note-Ilardi-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p><p>In 1762, <a href="/wiki/Leonhard_Euler" title="Leonhard Euler">Leonhard Euler</a><sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> says with respect to telescopes that, "it is necessary likewise to furnish the inside of the tube with one or more diaphragms, perforated with a small circular aperture, the better to exclude all extraneous light." </p><p>In 1867, <a href="/wiki/D%C3%A9sir%C3%A9_van_Monckhoven" title="Désiré van Monckhoven">Désiré van Monckhoven</a>, in one of the earliest books on photographic optics,<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> draws a distinction betweens <i>stops</i> and <i>diaphragms</i> in photography, but not in optics, saying: </p> <dl><dd>"Let us see what takes place when the stop is removed from the lens to a proper distance. In this case the stop becomes a diaphragm.</dd> <dd>* In optics, <i>stop</i> and <i>diaphragm</i> are synonyms. But in photographic optics they are only so by an unfortunate confusion of language. The stop reduces the lens to its central aperture; the diaphragm, on the contrary, allows all the segments of the lens to act, but only on the different radiating points placed symmetrically and concentrically in relation to the axis of the lens, or of the system of lenses (of which the axis is, besides, in every case common)."</dd></dl> <p>This distinction was maintained in Wall's 1889 <i>Dictionary of Photography</i> (see figure), but disappeared after <a href="/wiki/Ernst_Abbe" title="Ernst Abbe">Ernst Abbe</a>'s theory of stops unified these concepts. </p><p>According to <a href="/wiki/Rudolf_Kingslake" title="Rudolf Kingslake">Rudolf Kingslake</a>,<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> the inventor of the iris diaphragm is unknown. Others credit <a href="/wiki/Joseph_Nic%C3%A9phore_Ni%C3%A9pce" class="mw-redirect" title="Joseph Nicéphore Niépce">Joseph Nicéphore Niépce</a> for this device, around 1820. J. H. Brown, a member of the <a href="/wiki/Royal_Microscopical_Society" title="Royal Microscopical Society">Royal Microscopical Society</a>, appears to have invented a popular improved iris diaphragm by 1867.<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> </p><p>Kingslake has more definite histories for some other diaphragm types, such as M. Noton's adjustable <i>cat eye</i> diaphragm of two sliding squares in 1856, and the Waterhouse stops of <a href="/wiki/John_Waterhouse_(astronomer)" title="John Waterhouse (astronomer)">John Waterhouse</a> in 1858. </p><p>The <a href="/wiki/Hamburg_Observatory" title="Hamburg Observatory">Hamburg Observatory</a>-Bergedorf location had a 60 cm (~23.6 inch) aperture <a href="/wiki/Great_refractor" title="Great refractor">Great Refractor</a> by Reposold and Steinheil (Lenses).<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> One unique feature of the Hamburg Great Refractor is an iris diaphragm that allows the aperture to be adjusted from 5 to 60 cm.<sup id="cite_ref-:2_11-0" class="reference"><a href="#cite_note-:2-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> This telescope was activated in the early 1910s.<sup id="cite_ref-:2_11-1" class="reference"><a href="#cite_note-:2-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </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=Diaphragm_(optics)&action=edit&section=3" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Aperture" title="Aperture">Aperture</a></li> <li><a href="/wiki/F-number" title="F-number">f-number</a></li> <li><a href="/wiki/Shutter_(photography)" title="Shutter (photography)">Shutter (photography)</a></li> <li><a href="/wiki/Leaf_shutter" class="mw-redirect" title="Leaf shutter">Leaf shutter</a></li> <li><a href="/wiki/Diffraction_spike#Diffraction_spikes_due_to_non-circular_aperture" title="Diffraction spike">Diffraction spike</a></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=Diaphragm_(optics)&action=edit&section=4" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></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 mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text">Louis Derr, Photography for students of physics and chemistry London: The Macmillan Co., 1906</span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></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 class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.edmundoptics.com/c/iris-diaphragms/649/#">"Iris Diaphragms - Iris Diaphragm | Edmund Optics"</a>. <i>www.edmundoptics.com</i><span class="reference-accessdate">. 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Plume. p. <a rel="nofollow" class="external text" href="https://archive.org/details/filmmakershandbo00asch_0/page/154">154</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-452-28678-8" title="Special:BookSources/978-0-452-28678-8"><bdi>978-0-452-28678-8</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+Filmmaker%27s+Handbook%3A+A+Comprehensive+Guide+for+the+Digital+Age&rft.pages=154&rft.pub=Plume&rft.date=2007&rft.isbn=978-0-452-28678-8&rft.au=Steven+Ascher&rft.au=Edward+Pincus&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Ffilmmakershandbo00asch_0&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADiaphragm+%28optics%29" class="Z3988"></span></span> </li> <li id="cite_note-Ilardi-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-Ilardi_5-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFIlardi2007" class="citation book cs1">Ilardi, Vincent (2007). <a rel="nofollow" class="external text" href="https://archive.org/details/bub_gb_peIL7hVQUmwC"><i>Renaissance Vision from Spectacles to Telescopes</i></a>. 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Meissner, <i>Bericht über die Fortschritte der Anatomie und Physiologie im Jahre 1867</i>, Liepzip: C. F. Winter'sche Verlagshandlung, 1868.</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 class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.hs.uni-hamburg.de/DE/Oef/Stw/anderson/Move%20to%20Bergedorf.htm">"A SHORT HISTORY OF HAMBURG OBSERVATORY"</a>. <i>www.hs.uni-hamburg.de</i><span class="reference-accessdate">. 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