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contrast</span> </div> </a> <ul id="toc-Michelson_contrast-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-RMS_contrast" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#RMS_contrast"> <div class="vector-toc-text"> <span class="vector-toc-numb">2.3</span> <span>RMS contrast</span> </div> </a> <ul id="toc-RMS_contrast-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Contrast_sensitivity" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Contrast_sensitivity"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Contrast sensitivity</span> </div> </a> <button aria-controls="toc-Contrast_sensitivity-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Contrast sensitivity subsection</span> </button> <ul id="toc-Contrast_sensitivity-sublist" class="vector-toc-list"> <li id="toc-Contrast_sensitivity_and_visual_acuity" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Contrast_sensitivity_and_visual_acuity"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Contrast sensitivity and visual acuity</span> </div> </a> <ul id="toc-Contrast_sensitivity_and_visual_acuity-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Contrast_threshold" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Contrast_threshold"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Contrast threshold</span> </div> </a> <ul id="toc-Contrast_threshold-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Test_images" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Test_images"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Test images</span> </div> </a> <ul id="toc-Test_images-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">6</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">7</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>External links</span> </div> </a> <ul id="toc-External_links-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" > <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">Contrast (vision)</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 34 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-34" 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">34 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/Kontras_(visie)" title="Kontras (visie) – Afrikaans" lang="af" hreflang="af" data-title="Kontras (visie)" 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%AA%D8%A8%D8%A7%D9%8A%D9%86_(%D8%A8%D8%B5%D8%B1%D9%8A%D8%A7%D8%AA)" title="تباين (بصريات) – Arabic" lang="ar" hreflang="ar" data-title="تباين (بصريات)" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%9A%D0%B0%D0%BD%D1%82%D1%80%D0%B0%D1%81%D1%82" title="Кантраст – Belarusian" lang="be" hreflang="be" data-title="Кантраст" 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%9A%D0%BE%D0%BD%D1%82%D1%80%D0%B0%D1%81%D1%82" title="Контраст – Bulgarian" lang="bg" hreflang="bg" data-title="Контраст" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Contrast_(visi%C3%B3)" title="Contrast (visió) – Catalan" lang="ca" hreflang="ca" data-title="Contrast (visió)" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Kontrast_(lys)" title="Kontrast (lys) – Danish" lang="da" hreflang="da" data-title="Kontrast (lys)" 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/Kontrast" title="Kontrast – German" lang="de" hreflang="de" data-title="Kontrast" 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/Kontrastsus" title="Kontrastsus – Estonian" lang="et" hreflang="et" data-title="Kontrastsus" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Contraste" title="Contraste – Spanish" lang="es" hreflang="es" data-title="Contraste" 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/Kontrasto" title="Kontrasto – Esperanto" lang="eo" hreflang="eo" data-title="Kontrasto" 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/Kontraste" title="Kontraste – Basque" lang="eu" hreflang="eu" data-title="Kontraste" 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/%DA%A9%D9%86%D8%AA%D8%B1%D8%A7%D8%B3%D8%AA" title="کنتراست – Persian" lang="fa" hreflang="fa" data-title="کنتراست" 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/Contraste" title="Contraste – French" lang="fr" hreflang="fr" data-title="Contraste" 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/Codarsnacht" title="Codarsnacht – Irish" lang="ga" hreflang="ga" data-title="Codarsnacht" data-language-autonym="Gaeilge" data-language-local-name="Irish" class="interlanguage-link-target"><span>Gaeilge</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Contraste_(visi%C3%B3n)" title="Contraste (visión) – Galician" lang="gl" hreflang="gl" data-title="Contraste (visión)" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target"><span>Galego</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EB%8C%80%EB%B9%84_(%EA%B7%B8%EB%A6%BC)" title="대비 (그림) – Korean" lang="ko" hreflang="ko" data-title="대비 (그림)" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Kontras_(penglihatan)" title="Kontras (penglihatan) – Indonesian" lang="id" hreflang="id" data-title="Kontras (penglihatan)" 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/Contrasto" title="Contrasto – Italian" lang="it" hreflang="it" data-title="Contrasto" 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%A0%D7%99%D7%92%D7%95%D7%93%D7%99%D7%95%D7%AA" title="ניגודיות – Hebrew" lang="he" hreflang="he" data-title="ניגודיות" 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%9A%D0%BE%D0%BD%D1%82%D1%80%D0%B0%D1%81%D1%82" title="Контраст – Kyrgyz" lang="ky" hreflang="ky" data-title="Контраст" data-language-autonym="Кыргызча" data-language-local-name="Kyrgyz" class="interlanguage-link-target"><span>Кыргызча</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Kontras_(penglihatan)" title="Kontras (penglihatan) – Malay" lang="ms" hreflang="ms" data-title="Kontras (penglihatan)" 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/Contrast" title="Contrast – Dutch" lang="nl" hreflang="nl" data-title="Contrast" 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/%E3%82%B3%E3%83%B3%E3%83%88%E3%83%A9%E3%82%B9%E3%83%88" title="コントラスト – Japanese" lang="ja" hreflang="ja" data-title="コントラスト" 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/Kontrast_(lys)" title="Kontrast (lys) – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Kontrast (lys)" 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-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Kontrastowo%C5%9B%C4%87" title="Kontrastowość – Polish" lang="pl" hreflang="pl" data-title="Kontrastowość" 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/Contraste" title="Contraste – Portuguese" lang="pt" hreflang="pt" data-title="Contraste" 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/Contrast" title="Contrast – Romanian" lang="ro" hreflang="ro" data-title="Contrast" 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%9A%D0%BE%D0%BD%D1%82%D1%80%D0%B0%D1%81%D1%82" title="Контраст – Russian" lang="ru" hreflang="ru" data-title="Контраст" 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/Kontrasti" title="Kontrasti – Albanian" lang="sq" hreflang="sq" data-title="Kontrasti" data-language-autonym="Shqip" data-language-local-name="Albanian" class="interlanguage-link-target"><span>Shqip</span></a></li><li class="interlanguage-link interwiki-scn mw-list-item"><a href="https://scn.wikipedia.org/wiki/Cuntrastu" title="Cuntrastu – Sicilian" lang="scn" hreflang="scn" data-title="Cuntrastu" data-language-autonym="Sicilianu" data-language-local-name="Sicilian" class="interlanguage-link-target"><span>Sicilianu</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Kontrast" title="Kontrast – Swedish" lang="sv" hreflang="sv" data-title="Kontrast" 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%B8%84%E0%B8%A7%E0%B8%B2%E0%B8%A1%E0%B9%80%E0%B8%9B%E0%B8%A3%E0%B8%B5%E0%B8%A2%E0%B8%9A%E0%B8%95%E0%B9%88%E0%B8%B2%E0%B8%87" title="ความเปรียบต่าง – Thai" lang="th" hreflang="th" data-title="ความเปรียบต่าง" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%9A%D0%BE%D0%BD%D1%82%D1%80%D0%B0%D1%81%D1%82" title="Контраст – Ukrainian" lang="uk" hreflang="uk" data-title="Контраст" 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/%D9%85%D8%B9%D8%A7%DA%A9%D8%B3%DB%81_(%D8%A8%D8%B5%D8%A7%D8%B1%D8%AA)" title="معاکسہ (بصارت) – Urdu" lang="ur" hreflang="ur" data-title="معاکسہ (بصارت)" data-language-autonym="اردو" data-language-local-name="Urdu" class="interlanguage-link-target"><span>اردو</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/Q690182#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 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.mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">For other uses, see <a href="/wiki/Contrast_(disambiguation)" class="mw-redirect mw-disambig" title="Contrast (disambiguation)">Contrast</a>.</div><figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Contrast_change_photoshop.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/20/Contrast_change_photoshop.jpg/220px-Contrast_change_photoshop.jpg" decoding="async" width="220" height="247" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/20/Contrast_change_photoshop.jpg/330px-Contrast_change_photoshop.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/20/Contrast_change_photoshop.jpg/440px-Contrast_change_photoshop.jpg 2x" data-file-width="800" data-file-height="899" /></a><figcaption>Six renditions of a <a href="/wiki/Rocky_shore" title="Rocky shore">rocky shore</a> photo with incremental contrast levels, clockwise from bottom left</figcaption></figure><p><b>Contrast</b> is the difference in <a href="/wiki/Luminance" title="Luminance">luminance</a> or <a href="/wiki/Color" title="Color">color</a> that makes an object (or its representation in an image or display) visible against a background of different luminance or color.<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> The human <a href="/wiki/Visual_perception" title="Visual perception">visual system</a> is more sensitive to contrast than to absolute luminance; thus, we can perceive the world similarly despite significant changes in illumination throughout the day or across different locations.<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>The maximum contrast of an image is termed the <a href="/wiki/Contrast_ratio" title="Contrast ratio">contrast ratio</a> or <a href="/wiki/Dynamic_range" title="Dynamic range">dynamic range</a>. In images where the contrast ratio approaches the maximum possible for the medium, there is a <i>conservation of contrast</i>. In such cases, increasing contrast in certain parts of the image will necessarily result in a decrease in contrast elsewhere. Brightening an image increases contrast in darker areas but decreases it in brighter areas; conversely, darkening the image will have the opposite effect. <a href="/wiki/Bleach_bypass" title="Bleach bypass">Bleach bypass</a> reduces contrast in the darkest and brightest parts of an image while enhancing luminance contrast in areas of intermediate <a href="/wiki/Brightness" title="Brightness">brightness</a>. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Biological_contrast_sensitivity">Biological contrast sensitivity</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Contrast_(vision)&action=edit&section=1" title="Edit section: Biological contrast sensitivity"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div><p> Campbell and Robson (1968) showed that the human <a href="#Contrast_sensitivity">contrast sensitivity function</a> shows a typical <a href="/wiki/Band-pass_filter" title="Band-pass filter">band-pass filter</a> shape peaking at around 4 cycles per degree (cpd <i>or</i> cyc/deg), with sensitivity dropping off either side of the peak.<sup id="cite_ref-Campbell@1968_3-0" class="reference"><a href="#cite_note-Campbell@1968-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> This can be observed by changing one's viewing distance from a "sweep <a href="/wiki/Grating#Optical_grating" title="Grating">grating</a>" (shown below) showing many bars of a <a href="/wiki/Sine_wave" title="Sine wave">sinusoidal</a> grating that go from high to low contrast along the bars, and go from narrow (high spatial frequency) to wide (low spatial frequency) bars across the width of the grating. </p><figure typeof="mw:File/Thumb"><a href="/wiki/File:Photo_editing_contrast_correction.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/b/be/Photo_editing_contrast_correction.jpg/300px-Photo_editing_contrast_correction.jpg" decoding="async" width="300" height="225" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/be/Photo_editing_contrast_correction.jpg/450px-Photo_editing_contrast_correction.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/be/Photo_editing_contrast_correction.jpg/600px-Photo_editing_contrast_correction.jpg 2x" data-file-width="1024" data-file-height="768" /></a><figcaption>The contrast in the left half of the image is lower than that in the right half.</figcaption></figure> <p>The high-frequency cut-off represents the <a href="/wiki/Optics" title="Optics">optical</a> limitations of the visual system's ability to <a href="/wiki/Optical_resolution" title="Optical resolution">resolve</a> detail and is typically about 60 cpd. The high-frequency cut-off is also related to the packing density of the <a href="/wiki/Retina" title="Retina">retinal</a> <a href="/wiki/Photoreceptor_cell" title="Photoreceptor cell">photoreceptor cells</a>: a finer matrix can resolve finer gratings. </p><p>The low frequency drop-off is due to <a href="/wiki/Lateral_inhibition" title="Lateral inhibition">lateral inhibition</a> within the <a href="/wiki/Retinal_ganglion_cell" title="Retinal ganglion cell">retinal ganglion cells</a>.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> A typical retinal ganglion cell's <a href="/wiki/Receptive_field" title="Receptive field">receptive field</a> comprises a central region in which light either excites or inhibits the cell, and a surround region in which light has the opposite effects. </p><p>One experimental phenomenon is the inhibition of blue in the periphery if blue light is displayed against white, leading to a yellow surrounding. The yellow is derived from the inhibition of blue on the surroundings by the center. Since white minus blue is red and green, this mixes to become yellow.<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>For example, <a href="/wiki/Display_contrast" title="Display contrast">in the case of graphical computer displays</a>, contrast depends on the properties of the picture source or file and the properties of the computer display, including its variable settings. For some screens <a href="/wiki/Viewing_cone" title="Viewing cone">the angle</a> between the screen surface and the observer's line of sight is also important. </p> <div class="mw-heading mw-heading2"><h2 id="Quantifications">Quantifications</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Contrast_(vision)&action=edit&section=2" title="Edit section: Quantifications"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Further information: <a href="/wiki/Display_contrast" title="Display contrast">Display contrast</a></div> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Tour_Eiffel_Notre-Dame.JPG" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Tour_Eiffel_Notre-Dame.JPG/300px-Tour_Eiffel_Notre-Dame.JPG" decoding="async" width="300" height="200" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Tour_Eiffel_Notre-Dame.JPG/450px-Tour_Eiffel_Notre-Dame.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/83/Tour_Eiffel_Notre-Dame.JPG/600px-Tour_Eiffel_Notre-Dame.JPG 2x" data-file-width="3072" data-file-height="2048" /></a><figcaption>An image of the Notre Dame cathedral as seen from the <a href="/wiki/Eiffel_Tower" title="Eiffel Tower">Eiffel Tower</a></figcaption></figure> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Tour_Eiffel_Notre-Dame%2Bcontrast.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b9/Tour_Eiffel_Notre-Dame%2Bcontrast.jpg/300px-Tour_Eiffel_Notre-Dame%2Bcontrast.jpg" decoding="async" width="300" height="200" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b9/Tour_Eiffel_Notre-Dame%2Bcontrast.jpg/450px-Tour_Eiffel_Notre-Dame%2Bcontrast.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b9/Tour_Eiffel_Notre-Dame%2Bcontrast.jpg/600px-Tour_Eiffel_Notre-Dame%2Bcontrast.jpg 2x" data-file-width="3072" data-file-height="2048" /></a><figcaption>The same image, with added global contrast, and local contrast (<a href="/wiki/Acutance" title="Acutance">acutance</a>) increased through <a href="/wiki/Unsharp_masking" title="Unsharp masking">unsharp masking</a></figcaption></figure><p>There are many possible definitions of contrast. Some include color; others do not. Russian scientist <a href="/w/index.php?title=N._P._Travnikova&action=edit&redlink=1" class="new" title="N. P. Travnikova (page does not exist)">N. P. Travnikova</a><span class="noprint" style="font-size:85%; font-style: normal;"> [<a href="https://www.wikidata.org/wiki/Special:EntityPage/Q124308529#sitelinks-wikipedia" class="extiw" title="d:Special:EntityPage/Q124308529"><span title=""N. P. Travnikova" in other languages">d</span></a>]</span> laments, "Such a multiplicity of notions of contrast is extremely inconvenient. It complicates the solution of many applied problems and makes it difficult to compare the results published by different authors."<sup id="cite_ref-Peli1990_6-0" class="reference"><a href="#cite_note-Peli1990-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup><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> </p><p>Various definitions of contrast are used in different situations. Here, <a href="/wiki/Luminance" title="Luminance">luminance</a> contrast is used as an example, but the formulas can also be applied to other physical quantities. In many cases, the definitions of contrast represent a ratio of the type </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 {\mbox{Luminance difference}}{\mbox{Average luminance}}}.}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mstyle displaystyle="false" scriptlevel="0"> <mtext>Luminance difference</mtext> </mstyle> <mstyle displaystyle="false" scriptlevel="0"> <mtext>Average luminance</mtext> </mstyle> </mfrac> </mrow> <mo>.</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\frac {\mbox{Luminance difference}}{\mbox{Average luminance}}}.}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b4aad56885b55bc752770b1065c59a8fa5a0db04" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:22.901ex; height:6.009ex;" alt="{\displaystyle {\frac {\mbox{Luminance difference}}{\mbox{Average luminance}}}.}"></span></dd></dl> <p>The rationale behind this is that a small difference is negligible if the average luminance is high, while the same small difference matters if the average luminance is low (see <a href="/wiki/Weber%E2%80%93Fechner_law" title="Weber–Fechner law">Weber–Fechner law</a>). Below, some common definitions are given. </p> <div class="mw-heading mw-heading3"><h3 id="Weber_contrast">Weber contrast</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Contrast_(vision)&action=edit&section=3" title="Edit section: Weber contrast"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Weber contrast is defined as<sup id="cite_ref-Peli1990_6-1" class="reference"><a href="#cite_note-Peli1990-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </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 {I-I_{\mathrm {b} }}{I_{\mathrm {b} }}},}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mi>I</mi> <mo>−</mo> <msub> <mi>I</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">b</mi> </mrow> </mrow> </msub> </mrow> <msub> <mi>I</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">b</mi> </mrow> </mrow> </msub> </mfrac> </mrow> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\frac {I-I_{\mathrm {b} }}{I_{\mathrm {b} }}},}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d1d2a408ff570ccbc0e538e696e9fd34ebf86808" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.338ex; width:7.664ex; height:5.676ex;" alt="{\displaystyle {\frac {I-I_{\mathrm {b} }}{I_{\mathrm {b} }}},}"></span></dd></dl><p> with <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 I}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>I</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle I}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/535ea7fc4134a31cbe2251d9d3511374bc41be9f" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.172ex; height:2.176ex;" alt="{\displaystyle I}"></span> and <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 I_{\mathrm {b} }}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>I</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">b</mi> </mrow> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle I_{\mathrm {b} }}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3a4e79a9c1cf7c7d7229115d3c91d7b77110f17d" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.169ex; height:2.509ex;" alt="{\displaystyle I_{\mathrm {b} }}"></span> representing the luminance of the features and the background, respectively. The measure is also referred to as <i>Weber fraction</i>, since it is the term that is constant in <a href="/wiki/Weber%27s_Law" class="mw-redirect" title="Weber's Law">Weber's Law</a>. Weber contrast is commonly used in cases where small features are present on a large uniform background, i.e., where the average luminance is approximately equal to the background luminance.<style data-mw-deduplicate="TemplateStyles:r1237032888/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 img{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .tmulti .multiimageinner img{background-color:white}}</style></p><div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="width:244px;max-width:244px"><div class="trow"><div class="tsingle" style="width:242px;max-width:242px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Multi-color_leaf_without_saturation.jpg" class="mw-file-description"><img alt="A hand holding a multi-color leaf" src="//upload.wikimedia.org/wikipedia/commons/thumb/8/80/Multi-color_leaf_without_saturation.jpg/240px-Multi-color_leaf_without_saturation.jpg" decoding="async" width="240" height="320" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/80/Multi-color_leaf_without_saturation.jpg/360px-Multi-color_leaf_without_saturation.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/80/Multi-color_leaf_without_saturation.jpg/480px-Multi-color_leaf_without_saturation.jpg 2x" data-file-width="2448" data-file-height="3264" /></a></span></div></div></div><div class="trow"><div class="tsingle" style="width:242px;max-width:242px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Multi-color_leaf_with_saturation.jpg" class="mw-file-description"><img alt="The same image with greater contrast and saturation" src="//upload.wikimedia.org/wikipedia/commons/thumb/6/6c/Multi-color_leaf_with_saturation.jpg/240px-Multi-color_leaf_with_saturation.jpg" decoding="async" width="240" height="271" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/6c/Multi-color_leaf_with_saturation.jpg/360px-Multi-color_leaf_with_saturation.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/6c/Multi-color_leaf_with_saturation.jpg/480px-Multi-color_leaf_with_saturation.jpg 2x" data-file-width="1024" data-file-height="1156" /></a></span></div><div class="thumbcaption">A photograph of a leaf with several colors—the bottom image has an 11% saturation boost and around 10% increase in contrast.</div></div></div></div></div> <div class="mw-heading mw-heading3"><h3 id="Michelson_contrast">Michelson contrast</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Contrast_(vision)&action=edit&section=4" title="Edit section: Michelson contrast"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Michelson contrast<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> (also known as the <i>visibility</i>) is commonly used for patterns where both bright and dark features are equivalent and take up similar fractions of the area (e.g. <a href="/wiki/Spatial_frequency" title="Spatial frequency">sine-wave gratings</a>). The Michelson contrast is defined as<sup id="cite_ref-Peli1990_6-2" class="reference"><a href="#cite_note-Peli1990-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </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 {I_{\mathrm {max} }-I_{\mathrm {min} }}{I_{\mathrm {max} }+I_{\mathrm {min} }}},}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <msub> <mi>I</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">m</mi> <mi mathvariant="normal">a</mi> <mi mathvariant="normal">x</mi> </mrow> </mrow> </msub> <mo>−</mo> <msub> <mi>I</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">m</mi> <mi mathvariant="normal">i</mi> <mi mathvariant="normal">n</mi> </mrow> </mrow> </msub> </mrow> <mrow> <msub> <mi>I</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">m</mi> <mi mathvariant="normal">a</mi> <mi mathvariant="normal">x</mi> </mrow> </mrow> </msub> <mo>+</mo> <msub> <mi>I</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">m</mi> <mi mathvariant="normal">i</mi> <mi mathvariant="normal">n</mi> </mrow> </mrow> </msub> </mrow> </mfrac> </mrow> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\frac {I_{\mathrm {max} }-I_{\mathrm {min} }}{I_{\mathrm {max} }+I_{\mathrm {min} }}},}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/2f75b0dabafc3852c0b9c33efe7bd5235ed0aef2" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.338ex; width:12.633ex; height:5.676ex;" alt="{\displaystyle {\frac {I_{\mathrm {max} }-I_{\mathrm {min} }}{I_{\mathrm {max} }+I_{\mathrm {min} }}},}"></span></dd></dl> <p>with <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 I_{\mathrm {max} }}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>I</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">m</mi> <mi mathvariant="normal">a</mi> <mi mathvariant="normal">x</mi> </mrow> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle I_{\mathrm {max} }}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b2e3ae131f4cb6a62441f4beedeef61c6b76f932" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:4.314ex; height:2.509ex;" alt="{\displaystyle I_{\mathrm {max} }}"></span> and <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 I_{\mathrm {min} }}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>I</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">m</mi> <mi mathvariant="normal">i</mi> <mi mathvariant="normal">n</mi> </mrow> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle I_{\mathrm {min} }}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/c47d42e240ac362f0d0f90f6a5dd87d4392c7a67" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:3.996ex; height:2.509ex;" alt="{\displaystyle I_{\mathrm {min} }}"></span> representing the highest and lowest luminance. The denominator represents twice the average of the maximum and minimum luminances.<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>This form of contrast is an effective way to quantify contrast for periodic functions <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(x)}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>f</mi> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle f(x)}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/202945cce41ecebb6f643f31d119c514bec7a074" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:4.418ex; height:2.843ex;" alt="{\displaystyle f(x)}"></span> and is also known as the modulation <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 m_{f}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>m</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>f</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle m_{f}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a6b1ed1cca247d7fbe5a237f3c266a4e13850185" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:3.177ex; height:2.343ex;" alt="{\displaystyle m_{f}}"></span> of a periodic signal <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}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>f</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle f}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/132e57acb643253e7810ee9702d9581f159a1c61" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:1.279ex; height:2.509ex;" alt="{\displaystyle f}"></span>. Modulation quantifies the relative amount by which the amplitude (or difference) <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_{\text{max}}-f_{\text{min}})/2}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mo stretchy="false">(</mo> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>max</mtext> </mrow> </msub> <mo>−</mo> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>min</mtext> </mrow> </msub> <mo stretchy="false">)</mo> <mrow class="MJX-TeXAtom-ORD"> <mo>/</mo> </mrow> <mn>2</mn> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle (f_{\text{max}}-f_{\text{min}})/2}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b347dd7b25a28be6fa3ab57a47e4b2df0b241023" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:15.517ex; height:2.843ex;" alt="{\displaystyle (f_{\text{max}}-f_{\text{min}})/2}"></span> of <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}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>f</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle f}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/132e57acb643253e7810ee9702d9581f159a1c61" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:1.279ex; height:2.509ex;" alt="{\displaystyle f}"></span> stands out from the average value (or background) <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_{\text{max}}+f_{\text{min}})/2}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mo stretchy="false">(</mo> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>max</mtext> </mrow> </msub> <mo>+</mo> <msub> <mi>f</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>min</mtext> </mrow> </msub> <mo stretchy="false">)</mo> <mrow class="MJX-TeXAtom-ORD"> <mo>/</mo> </mrow> <mn>2</mn> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle (f_{\text{max}}+f_{\text{min}})/2}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d134a7477c36219ee3ad8bdb72724ae1b3cae0f8" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:15.517ex; height:2.843ex;" alt="{\displaystyle (f_{\text{max}}+f_{\text{min}})/2}"></span>. </p><p>In general, <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 m_{f}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>m</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>f</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle m_{f}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a6b1ed1cca247d7fbe5a237f3c266a4e13850185" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:3.177ex; height:2.343ex;" alt="{\displaystyle m_{f}}"></span> refers to the contrast of the periodic signal <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}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>f</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle f}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/132e57acb643253e7810ee9702d9581f159a1c61" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:1.279ex; height:2.509ex;" alt="{\displaystyle f}"></span> relative to its average value. If <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 m_{f}=0}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>m</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>f</mi> </mrow> </msub> <mo>=</mo> <mn>0</mn> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle m_{f}=0}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a88ece180fcfdf014d5a4423777584f58b8dcc6f" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:7.438ex; height:2.843ex;" alt="{\displaystyle m_{f}=0}"></span>, then <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}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>f</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle f}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/132e57acb643253e7810ee9702d9581f159a1c61" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:1.279ex; height:2.509ex;" alt="{\displaystyle f}"></span> has no contrast. If two periodic functions <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}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>f</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle f}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/132e57acb643253e7810ee9702d9581f159a1c61" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:1.279ex; height:2.509ex;" alt="{\displaystyle f}"></span> and <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 g}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>g</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle g}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d3556280e66fe2c0d0140df20935a6f057381d77" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:1.116ex; height:2.009ex;" alt="{\displaystyle g}"></span> have the same average value, then <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}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>f</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle f}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/132e57acb643253e7810ee9702d9581f159a1c61" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:1.279ex; height:2.509ex;" alt="{\displaystyle f}"></span> has more contrast than <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 g}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>g</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle g}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d3556280e66fe2c0d0140df20935a6f057381d77" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:1.116ex; height:2.009ex;" alt="{\displaystyle g}"></span> if <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 m_{f}>m_{g}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>m</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>f</mi> </mrow> </msub> <mo>></mo> <msub> <mi>m</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>g</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle m_{f}>m_{g}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7fc29320e25442e4de59abbbed0793e286759170" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:9.337ex; height:2.509ex;" alt="{\displaystyle m_{f}>m_{g}}"></span>.<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> <div class="mw-heading mw-heading3"><h3 id="RMS_contrast">RMS contrast</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Contrast_(vision)&action=edit&section=5" title="Edit section: RMS contrast"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Root_mean_square" title="Root mean square">Root mean square</a> (RMS) contrast does not depend on the spatial frequency content or the spatial distribution of contrast in the image. RMS contrast is defined as the standard deviation of the <a href="/wiki/Pixel" title="Pixel">pixel</a> intensities:<sup id="cite_ref-Peli1990_6-3" class="reference"><a href="#cite_note-Peli1990-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </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 {\sqrt {{\frac {1}{MN}}\sum _{i=0}^{N-1}\sum _{j=0}^{M-1}\left(I_{ij}-{\bar {I}}\right)^{2}}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <msqrt> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <mrow> <mi>M</mi> <mi>N</mi> </mrow> </mfrac> </mrow> <munderover> <mo>∑</mo> <mrow class="MJX-TeXAtom-ORD"> <mi>i</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mi>N</mi> <mo>−</mo> <mn>1</mn> </mrow> </munderover> <munderover> <mo>∑</mo> <mrow class="MJX-TeXAtom-ORD"> <mi>j</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mi>M</mi> <mo>−</mo> <mn>1</mn> </mrow> </munderover> <msup> <mrow> <mo>(</mo> <mrow> <msub> <mi>I</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>i</mi> <mi>j</mi> </mrow> </msub> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mover> <mi>I</mi> <mo stretchy="false">¯</mo> </mover> </mrow> </mrow> </mrow> <mo>)</mo> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> </msqrt> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\sqrt {{\frac {1}{MN}}\sum _{i=0}^{N-1}\sum _{j=0}^{M-1}\left(I_{ij}-{\bar {I}}\right)^{2}}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/620c41377e48a6e3f680f14bc49f532446e5d67f" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -3.338ex; width:26.39ex; height:8.343ex;" alt="{\displaystyle {\sqrt {{\frac {1}{MN}}\sum _{i=0}^{N-1}\sum _{j=0}^{M-1}\left(I_{ij}-{\bar {I}}\right)^{2}}}}"></span></dd></dl> <p>where intensities <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 I_{ij}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>I</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>i</mi> <mi>j</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle I_{ij}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/b8e861c28675994decc6373478cade6f99e4f4df" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:2.5ex; height:2.843ex;" alt="{\displaystyle I_{ij}}"></span> are the <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 i}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>i</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle i}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/add78d8608ad86e54951b8c8bd6c8d8416533d20" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:0.802ex; height:2.176ex;" alt="{\displaystyle i}"></span>-th <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 j}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>j</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle j}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/2f461e54f5c093e92a55547b9764291390f0b5d0" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; margin-left: -0.027ex; width:0.985ex; height:2.509ex;" alt="{\displaystyle j}"></span>-th element of the two-dimensional image of size <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 M}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>M</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle M}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f82cade9898ced02fdd08712e5f0c0151758a0dd" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.442ex; height:2.176ex;" alt="{\displaystyle M}"></span> by <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 N}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>N</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle N}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f5e3890c981ae85503089652feb48b191b57aae3" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.064ex; height:2.176ex;" alt="{\displaystyle N}"></span>. <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 {\bar {I}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mover> <mi>I</mi> <mo stretchy="false">¯</mo> </mover> </mrow> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\bar {I}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ab2ee9e7dd5523b6c8794be941a43f52a3063199" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.522ex; height:2.509ex;" alt="{\displaystyle {\bar {I}}}"></span> is the average intensity of all pixel values in the image. The image <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 I}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>I</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle I}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/535ea7fc4134a31cbe2251d9d3511374bc41be9f" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.172ex; height:2.176ex;" alt="{\displaystyle I}"></span> is assumed to have its pixel intensities normalized in the range <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 [0,1]}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mo stretchy="false">[</mo> <mn>0</mn> <mo>,</mo> <mn>1</mn> <mo stretchy="false">]</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle [0,1]}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/738f7d23bb2d9642bab520020873cccbef49768d" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:4.653ex; height:2.843ex;" alt="{\displaystyle [0,1]}"></span>. </p> <div class="mw-heading mw-heading2"><h2 id="Contrast_sensitivity">Contrast sensitivity</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Contrast_(vision)&action=edit&section=6" title="Edit section: Contrast sensitivity"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><i>Contrast sensitivity</i> is a measure of the ability to discern different <a href="/wiki/Luminance" title="Luminance">luminances</a> in a static <a href="/wiki/Image" title="Image">image</a>. It varies with age, increasing to a maximum around 20 years at <a href="/wiki/Spatial_frequency" title="Spatial frequency">spatial frequencies</a> of about 2–5 cpd; aging then progressively attenuates contrast sensitivity beyond this peak. Factors such as cataracts and <a href="/wiki/Diabetic_retinopathy" title="Diabetic retinopathy">diabetic retinopathy</a> also reduce contrast sensitivity.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> In the sweep grating figure below, at an ordinary viewing distance, the bars in the middle appear to be the longest due to their optimal spatial frequency. However, at a far viewing distance, the longest visible bars shift to what were originally the wide bars, now matching the spatial frequency of the middle bars at reading distance. </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:SinVibr.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/28/SinVibr.png/220px-SinVibr.png" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/28/SinVibr.png/330px-SinVibr.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/28/SinVibr.png/440px-SinVibr.png 2x" data-file-width="1024" data-file-height="768" /></a><figcaption>In this image of a "sweep grating", the contrast amplitude depends only on the vertical coordinate, and the spatial frequency depends only on the horizontal coordinate. For medium frequency, less contrast is needed than for high or low frequency to detect the bars.</figcaption></figure> <div class="mw-heading mw-heading3"><h3 id="Contrast_sensitivity_and_visual_acuity">Contrast sensitivity and visual acuity</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Contrast_(vision)&action=edit&section=7" title="Edit section: Contrast sensitivity and visual acuity"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Visual_acuity" title="Visual acuity">Visual acuity</a> is a parameter that is frequently used to assess overall vision. However, diminished contrast sensitivity may cause decreased visual function in spite of normal visual acuity.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> For example, some individuals with <a href="/wiki/Glaucoma" title="Glaucoma">glaucoma</a> may achieve 20/20 vision on acuity exams, yet struggle with <a href="/wiki/Activities_of_daily_living" title="Activities of daily living">activities of daily living</a>, such as driving at night. </p><p>As mentioned above, contrast sensitivity describes the ability of the visual system to distinguish bright and dim components of a static image. Visual acuity can be defined as the angle with which one can resolve two points as being separate since the image is shown with 100% contrast and is projected onto the fovea of the retina.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> Thus, when an <a href="/wiki/Optometrist" class="mw-redirect" title="Optometrist">optometrist</a> or <a href="/wiki/Ophthalmologist" class="mw-redirect" title="Ophthalmologist">ophthalmologist</a> assesses a patient's visual acuity using a <a href="/wiki/Snellen_chart" title="Snellen chart">Snellen chart</a> or some other <a href="/wiki/Landolt_C" title="Landolt C">acuity chart</a>, the target image is displayed at high contrast, e.g., black letters of decreasing size on a white background. A subsequent contrast sensitivity exam may demonstrate difficulty with decreased contrast (using, e.g., the Pelli–Robson chart, which consists of uniform-sized but increasingly pale grey letters on a white background). </p><p> To assess a patient's contrast sensitivity, one of several diagnostic exams may be used. Most charts in an ophthalmologist's or optometrist's office will show images of varying contrast and <a href="/wiki/Spatial_frequency" title="Spatial frequency">spatial frequency</a>. Parallel bars of varying width and contrast, known as sine-wave gratings, are sequentially viewed by the patient. The width of the bars and their distance apart represent spatial frequency, measured in cycles per degree.</p><figure class="mw-default-size mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Opponent_process_contrast_sensitivity_functions.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/8d/Opponent_process_contrast_sensitivity_functions.svg/220px-Opponent_process_contrast_sensitivity_functions.svg.png" decoding="async" width="220" height="264" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/8d/Opponent_process_contrast_sensitivity_functions.svg/330px-Opponent_process_contrast_sensitivity_functions.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/8d/Opponent_process_contrast_sensitivity_functions.svg/440px-Opponent_process_contrast_sensitivity_functions.svg.png 2x" data-file-width="512" data-file-height="614" /></a><figcaption>Log–log plot of spatial contrast sensitivity functions for luminance and chromatic contrast</figcaption></figure><p>Studies have demonstrated that contrast sensitivity is maximum for spatial frequencies of 2-5 cpd, falling off for lower spatial frequencies and rapidly falling off for higher spatial frequencies. The upper limit for the human vision system is about 60 cpd. The correct identification of small letters requires the letter size be about 18-30 cpd.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> <i>Contrast threshold</i> can be defined as the minimum contrast that can be resolved by the patient. Contrast sensitivity is typically expressed as the <a href="/wiki/Multiplicative_inverse" title="Multiplicative inverse">reciprocal</a> of the threshold contrast for detection of a given pattern (i.e., 1 ÷ contrast threshold).<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> </p><p>Using the results of a contrast sensitivity exam, a contrast sensitivity curve can be plotted, with spatial frequency on the horizontal, and contrast threshold on the vertical axis. Also known as contrast sensitivity function (CSF), the plot demonstrates the normal range of contrast sensitivity, and will indicate diminished contrast sensitivity in patients who fall below the normal curve. Some graphs contain "contrast sensitivity acuity equivalents", with lower acuity values falling in the area under the curve. In patients with normal visual acuity and concomitant reduced contrast sensitivity, the area under the curve serves as a graphical representation of the visual deficit. It can be because of this impairment in contrast sensitivity that patients have difficulty driving at night, climbing stairs and other activities of daily living in which contrast is reduced.<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> </p><p>Recent studies have demonstrated that intermediate-frequency sinusoidal patterns are optimally-detected by the retina due to the center-surround arrangement of neuronal receptive fields.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> In an intermediate spatial frequency, the peak (brighter bars) of the pattern is detected by the center of the receptive field, while the troughs (darker bars) are detected by the inhibitory periphery of the receptive field. For this reason, low- and high-spatial frequencies elicit excitatory and inhibitory impulses by overlapping frequency peaks and troughs in the center and periphery of the neuronal <a href="/wiki/Receptive_field" title="Receptive field">receptive field</a>.<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> Other environmental,<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> physiological, and anatomical factors influence the neuronal transmission of sinusoidal patterns, including <a href="/wiki/Adaptation" title="Adaptation">adaptation</a>.<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Contrast_Sensitivity_vs._Spacial_Frequency.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Contrast_Sensitivity_vs._Spacial_Frequency.png/220px-Contrast_Sensitivity_vs._Spacial_Frequency.png" decoding="async" width="220" height="166" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Contrast_Sensitivity_vs._Spacial_Frequency.png/330px-Contrast_Sensitivity_vs._Spacial_Frequency.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Contrast_Sensitivity_vs._Spacial_Frequency.png/440px-Contrast_Sensitivity_vs._Spacial_Frequency.png 2x" data-file-width="1024" data-file-height="771" /></a><figcaption>The graph demonstrates the relationship between contrast sensitivity and spatial frequency. The target-like images are representative of center-surround organization of neurons, with peripheral inhibition at low, intermediate and high spatial frequencies. <i>Used with permission from Brian Wandell, PhD</i>.</figcaption></figure> <p>Decreased contrast sensitivity arises from multiple etiologies, including retinal disorders such as <a href="/wiki/Age-related_macular_degeneration" class="mw-redirect" title="Age-related macular degeneration">age-related macular degeneration</a> (ARMD), <a href="/wiki/Amblyopia" title="Amblyopia">amblyopia</a>, lens abnormalities, such as <a href="/wiki/Cataract" title="Cataract">cataract</a>, and by higher-order neural dysfunction, including <a href="/wiki/Stroke" title="Stroke">stroke</a> and <a href="/wiki/Alzheimer%27s_disease" title="Alzheimer's disease">Alzheimer's disease</a>.<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> In light of the multitude of etiologies leading to decreased contrast sensitivity, contrast sensitivity tests are useful in the characterization and monitoring of dysfunction, and less helpful in detection of disease. </p> <div class="mw-heading mw-heading2"><h2 id="Contrast_threshold">Contrast threshold</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Contrast_(vision)&action=edit&section=8" title="Edit section: Contrast threshold"><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:CrumeyFig4.pdf" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/4d/CrumeyFig4.pdf/page1-220px-CrumeyFig4.pdf.jpg" decoding="async" width="220" height="174" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/4d/CrumeyFig4.pdf/page1-330px-CrumeyFig4.pdf.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/4d/CrumeyFig4.pdf/page1-440px-CrumeyFig4.pdf.jpg 2x" data-file-width="1350" data-file-height="1066" /></a><figcaption>Threshold data from Table 8 of Blackwell (1946)<sup id="cite_ref-blackwell_22-0" class="reference"><a href="#cite_note-blackwell-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> plotted as Figure 4 of <a href="/wiki/Andrew_Crumey" title="Andrew Crumey">Crumey</a> (2014).<sup id="cite_ref-crumey_23-0" class="reference"><a href="#cite_note-crumey-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> Curves are for background luminances ranging from 3.426 × 10<sup>−5</sup> cd m<sup>−2</sup> (top) to 3.426 × 10<sup>3</sup> cd m<sup>−2</sup> (bottom) at intervals of one log unit.</figcaption></figure> <p>A large-scale study of luminance contrast thresholds was done in the 1940s by Blackwell,<sup id="cite_ref-blackwell_22-1" class="reference"><a href="#cite_note-blackwell-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> using a forced-choice procedure. Discs of various sizes and luminances were presented in different positions against backgrounds at a wide range of adaptation luminances, and subjects had to indicate where they thought the disc was being shown. After statistical pooling of results (90,000 observations by seven observers), the threshold for a given target size and luminance was defined as the Weber contrast level at which there was a 50% detection level. The experiment employed a discrete set of contrast levels, resulting in discrete values of threshold contrast. Smooth curves were drawn through these, and values tabulated. The resulting data have been used extensively in areas such as lighting engineering and road safety.<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> </p><p>A separate study by Knoll et al<sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> investigated thresholds for point sources by requiring subjects to vary the brightness of the source to find the level at which it was just visible. A mathematical formula for the resulting threshold curve was proposed by <a href="/wiki/Selig_Hecht" title="Selig Hecht">Hecht</a>,<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> with separate branches for scotopic and photopic vision. Hecht's formula was used by Weaver<sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> to model the naked-eye visibility of stars. The same formula was used later by <a href="/wiki/Bradley_Schaefer" title="Bradley Schaefer">Schaefer</a><sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> to model stellar visibility through a telescope. </p><p><a href="/wiki/Andrew_Crumey" title="Andrew Crumey">Crumey</a><sup id="cite_ref-crumey_23-1" class="reference"><a href="#cite_note-crumey-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> showed that Hecht's formula fitted the data very poorly at low light levels, so was not really suitable for modelling stellar visibility. Crumey instead constructed a more accurate and general model applicable to both the Blackwell and Knoll et al data. Crumey's model covers all light levels, from zero background luminance to daylight levels, and instead of parameter-tuning is based on an underlying linearity related to <a href="/wiki/Ricco%27s_law" title="Ricco's law">Ricco's law</a>. Crumey used it to model astronomical visibility for targets of arbitrary size, and to study the effects of light pollution. </p> <div class="mw-heading mw-heading2"><h2 id="Test_images">Test images</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Contrast_(vision)&action=edit&section=9" title="Edit section: Test images"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Test images types<sup id="cite_ref-29" class="reference"><a href="#cite_note-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> </p> <ul><li>Pelli-Robson Contrast Sensitivity Chart</li> <li>Regan chart</li> <li>Arden grating chart</li> <li>Campbell-Robson Contrast Sensitivity Chart<sup id="cite_ref-30" class="reference"><a href="#cite_note-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup></li></ul> <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=Contrast_(vision)&action=edit&section=10" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1184024115">.mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}</style><div class="div-col" style="column-width: 20em;"> <ul><li><a href="/wiki/Acutance" title="Acutance">Acutance</a></li> <li><a href="/wiki/Color_blindness" title="Color blindness">Color blindness</a></li> <li><a href="/wiki/Contrast_ratio" title="Contrast ratio">Contrast ratio</a></li> <li><a href="/wiki/Display_contrast" title="Display contrast">Display contrast</a></li> <li><a href="/wiki/Eye_examination" title="Eye examination">Eye examination</a></li> <li><a href="/wiki/Optical_resolution" title="Optical resolution">Optical resolution</a></li> <li><a href="/wiki/Psychophysics" title="Psychophysics">Psychophysics</a></li> <li><a href="/wiki/Radiocontrast" class="mw-redirect" title="Radiocontrast">Radiocontrast</a></li> <li><a href="/wiki/Spatial_frequency" title="Spatial frequency">Spatial frequency</a></li> <li><a href="/wiki/Visual_acuity" title="Visual acuity">Visual acuity</a></li></ul> </div> <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=Contrast_(vision)&action=edit&section=11" 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"><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 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Last Update: June 11, 2023.</a></span> </li> <li id="cite_note-30"><span class="mw-cite-backlink"><b><a href="#cite_ref-30">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFTardifWatsonGiaschiGosselin2021" class="citation journal cs1">Tardif, Jessica; Watson, Marcus R.; Giaschi, Deborah; Gosselin, Frédéric (2021-03-09). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7985182">"The Curve Visible on the Campbell-Robson Chart Is Not the Contrast Sensitivity Function"</a>. <i>Frontiers in Neuroscience</i>. <b>15</b>. Frontiers Media SA. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.3389%2Ffnins.2021.626466">10.3389/fnins.2021.626466</a></span>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1662-453X">1662-453X</a>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7985182">7985182</a></span>. <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/33767608">33767608</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Frontiers+in+Neuroscience&rft.atitle=The+Curve+Visible+on+the+Campbell-Robson+Chart+Is+Not+the+Contrast+Sensitivity+Function&rft.volume=15&rft.date=2021-03-09&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC7985182%23id-name%3DPMC&rft.issn=1662-453X&rft_id=info%3Apmid%2F33767608&rft_id=info%3Adoi%2F10.3389%2Ffnins.2021.626466&rft.aulast=Tardif&rft.aufirst=Jessica&rft.au=Watson%2C+Marcus+R.&rft.au=Giaschi%2C+Deborah&rft.au=Gosselin%2C+Fr%C3%A9d%C3%A9ric&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC7985182&rfr_id=info%3Asid%2Fen.wikipedia.org%3AContrast+%28vision%29" class="Z3988"></span></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Contrast_(vision)&action=edit&section=12" 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