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class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#SI_photometric_light_units"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>SI photometric light units</span> </div> </a> <button aria-controls="toc-SI_photometric_light_units-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 SI photometric light units subsection</span> </button> <ul id="toc-SI_photometric_light_units-sublist" class="vector-toc-list"> <li id="toc-Relationships_between_luminous_intensity,_luminous_flux,_and_illuminance" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Relationships_between_luminous_intensity,_luminous_flux,_and_illuminance"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Relationships between luminous intensity, luminous flux, and illuminance</span> </div> </a> <ul id="toc-Relationships_between_luminous_intensity,_luminous_flux,_and_illuminance-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-SI_multiples" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#SI_multiples"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>SI multiples</span> </div> </a> <ul id="toc-SI_multiples-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Notes" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Notes"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Notes</span> </div> </a> <ul id="toc-Notes-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Table of Contents" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Candela</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 84 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-84" 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">84 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D9%82%D9%86%D8%AF%D9%8A%D9%84%D8%A9" title="قنديلة – Arabic" lang="ar" hreflang="ar" data-title="قنديلة" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-ast mw-list-item"><a href="https://ast.wikipedia.org/wiki/Candela" title="Candela – Asturian" lang="ast" hreflang="ast" data-title="Candela" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-az mw-list-item"><a href="https://az.wikipedia.org/wiki/Kandela" title="Kandela – Azerbaijani" lang="az" hreflang="az" data-title="Kandela" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target"><span>Azərbaycanca</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%95%E0%A7%8D%E0%A6%AF%E0%A6%BE%E0%A6%A8%E0%A7%8D%E0%A6%A1%E0%A7%87%E0%A6%B2%E0%A6%BE" title="ক্যান্ডেলা – Bangla" lang="bn" hreflang="bn" data-title="ক্যান্ডেলা" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-zh-min-nan mw-list-item"><a href="https://zh-min-nan.wikipedia.org/wiki/Candela" title="Candela – Minnan" lang="nan" hreflang="nan" data-title="Candela" data-language-autonym="閩南語 / Bân-lâm-gú" data-language-local-name="Minnan" class="interlanguage-link-target"><span>閩南語 / Bân-lâm-gú</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%D0%B4%D1%8D%D0%BB%D0%B0" title="Кандэла – Belarusian" lang="be" hreflang="be" data-title="Кандэла" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-be-x-old mw-list-item"><a href="https://be-tarask.wikipedia.org/wiki/%D0%9A%D0%B0%D0%BD%D0%B4%D1%8D%D0%BB%D0%B0" title="Кандэла – Belarusian (Taraškievica orthography)" lang="be-tarask" hreflang="be-tarask" data-title="Кандэла" data-language-autonym="Беларуская (тарашкевіца)" data-language-local-name="Belarusian (Taraškievica orthography)" class="interlanguage-link-target"><span>Беларуская (тарашкевіца)</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%9A%D0%B0%D0%BD%D0%B4%D0%B5%D0%BB%D0%B0" title="Кандела – Bulgarian" lang="bg" hreflang="bg" data-title="Кандела" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-bo mw-list-item"><a href="https://bo.wikipedia.org/wiki/%E0%BD%81%E0%BD%BA%E0%BD%93%E0%BC%8D" title="ཁེན། – Tibetan" lang="bo" hreflang="bo" data-title="ཁེན།" data-language-autonym="བོད་ཡིག" data-language-local-name="Tibetan" class="interlanguage-link-target"><span>བོད་ཡིག</span></a></li><li class="interlanguage-link interwiki-bs mw-list-item"><a href="https://bs.wikipedia.org/wiki/Kandela" title="Kandela – Bosnian" lang="bs" hreflang="bs" data-title="Kandela" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target"><span>Bosanski</span></a></li><li class="interlanguage-link interwiki-br mw-list-item"><a href="https://br.wikipedia.org/wiki/Candela" title="Candela – Breton" lang="br" hreflang="br" data-title="Candela" data-language-autonym="Brezhoneg" data-language-local-name="Breton" class="interlanguage-link-target"><span>Brezhoneg</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Candela" title="Candela – Catalan" lang="ca" hreflang="ca" data-title="Candela" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cv mw-list-item"><a href="https://cv.wikipedia.org/wiki/%D0%9A%D0%B0%D0%BD%D0%B4%D0%B5%D0%BB%D0%B0" title="Кандела – Chuvash" lang="cv" hreflang="cv" data-title="Кандела" data-language-autonym="Чӑвашла" data-language-local-name="Chuvash" class="interlanguage-link-target"><span>Чӑвашла</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Kandela" title="Kandela – Czech" lang="cs" hreflang="cs" data-title="Kandela" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-cy mw-list-item"><a href="https://cy.wikipedia.org/wiki/Candela" title="Candela – Welsh" lang="cy" hreflang="cy" data-title="Candela" data-language-autonym="Cymraeg" data-language-local-name="Welsh" class="interlanguage-link-target"><span>Cymraeg</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Candela" title="Candela – Danish" lang="da" hreflang="da" data-title="Candela" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-ary mw-list-item"><a href="https://ary.wikipedia.org/wiki/%D9%82%D9%86%D8%AF%D9%8A%D9%84%D8%A9" title="قنديلة – Moroccan Arabic" lang="ary" hreflang="ary" data-title="قنديلة" data-language-autonym="الدارجة" data-language-local-name="Moroccan Arabic" class="interlanguage-link-target"><span>الدارجة</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Candela" title="Candela – German" lang="de" hreflang="de" data-title="Candela" 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/Kandela" title="Kandela – Estonian" lang="et" hreflang="et" data-title="Kandela" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/%CE%9A%CE%B7%CF%81%CE%AF%CE%BF_(%CF%86%CF%85%CF%83%CE%B9%CE%BA%CE%AE)" title="Κηρίο (φυσική) – Greek" lang="el" hreflang="el" data-title="Κηρίο (φυσική)" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Candela" title="Candela – Spanish" lang="es" hreflang="es" data-title="Candela" 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/Kandelo_(mezurunuo)" title="Kandelo (mezurunuo) – Esperanto" lang="eo" hreflang="eo" data-title="Kandelo (mezurunuo)" 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/Kandela_(unitatea)" title="Kandela (unitatea) – Basque" lang="eu" hreflang="eu" data-title="Kandela (unitatea)" 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%B4%D9%85%D8%B9_(%DB%8C%DA%A9%D8%A7)" title="شمع (یکا) – Persian" lang="fa" hreflang="fa" data-title="شمع (یکا)" 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/Candela" title="Candela – French" lang="fr" hreflang="fr" data-title="Candela" 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/Caind%C3%A9ile" title="Caindéile – Irish" lang="ga" hreflang="ga" data-title="Caindéile" 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/Candela" title="Candela – Galician" lang="gl" hreflang="gl" data-title="Candela" 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/%EC%B9%B8%EB%8D%B8%EB%9D%BC" title="칸델라 – Korean" lang="ko" hreflang="ko" data-title="칸델라" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D4%BF%D5%A1%D5%B6%D5%A4%D5%A5%D5%AC%D5%A1" title="Կանդելա – Armenian" lang="hy" hreflang="hy" data-title="Կանդելա" data-language-autonym="Հայերեն" data-language-local-name="Armenian" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%95%E0%A5%88%E0%A4%82%E0%A4%A1%E0%A4%BF%E0%A4%B2%E0%A4%BE" title="कैंडिला – Hindi" lang="hi" hreflang="hi" data-title="कैंडिला" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Kandela" title="Kandela – Croatian" lang="hr" hreflang="hr" data-title="Kandela" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Kandela" title="Kandela – Indonesian" lang="id" hreflang="id" data-title="Kandela" 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-is mw-list-item"><a href="https://is.wikipedia.org/wiki/Kandela" title="Kandela – Icelandic" lang="is" hreflang="is" data-title="Kandela" data-language-autonym="Íslenska" data-language-local-name="Icelandic" class="interlanguage-link-target"><span>Íslenska</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Candela_(unit%C3%A0_di_misura)" title="Candela (unità di misura) – Italian" lang="it" hreflang="it" data-title="Candela (unità di misura)" 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%A7%D7%A0%D7%93%D7%9C%D7%94" title="קנדלה – Hebrew" lang="he" hreflang="he" data-title="קנדלה" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/%E1%83%99%E1%83%90%E1%83%9C%E1%83%93%E1%83%94%E1%83%9A%E1%83%90" title="კანდელა – Georgian" lang="ka" hreflang="ka" data-title="კანდელა" data-language-autonym="ქართული" data-language-local-name="Georgian" class="interlanguage-link-target"><span>ქართული</span></a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%9A%D0%B0%D0%BD%D0%B4%D0%B5%D0%BB%D0%B0" title="Кандела – Kazakh" lang="kk" hreflang="kk" data-title="Кандела" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target"><span>Қазақша</span></a></li><li class="interlanguage-link interwiki-ky mw-list-item"><a href="https://ky.wikipedia.org/wiki/%D0%9A%D0%B0%D0%BD%D0%B4%D0%B5%D0%BB%D0%B0" title="Кандела – Kyrgyz" lang="ky" hreflang="ky" data-title="Кандела" data-language-autonym="Кыргызча" data-language-local-name="Kyrgyz" class="interlanguage-link-target"><span>Кыргызча</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/Kandela" title="Kandela – Latvian" lang="lv" hreflang="lv" data-title="Kandela" data-language-autonym="Latviešu" data-language-local-name="Latvian" class="interlanguage-link-target"><span>Latviešu</span></a></li><li class="interlanguage-link interwiki-lb mw-list-item"><a href="https://lb.wikipedia.org/wiki/Candela" title="Candela – Luxembourgish" lang="lb" hreflang="lb" data-title="Candela" 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/Kandela" title="Kandela – Lithuanian" lang="lt" hreflang="lt" data-title="Kandela" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/Kandela" title="Kandela – Hungarian" lang="hu" hreflang="hu" data-title="Kandela" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target"><span>Magyar</span></a></li><li class="interlanguage-link interwiki-mk mw-list-item"><a href="https://mk.wikipedia.org/wiki/%D0%9A%D0%B0%D0%BD%D0%B4%D0%B5%D0%BB%D0%B0" title="Кандела – Macedonian" lang="mk" hreflang="mk" data-title="Кандела" data-language-autonym="Македонски" data-language-local-name="Macedonian" class="interlanguage-link-target"><span>Македонски</span></a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%95%E0%B4%BE%E0%B5%BB%E0%B4%A1%E0%B5%86%E0%B4%B2" title="കാൻഡെല – Malayalam" lang="ml" hreflang="ml" data-title="കാൻഡെല" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Kandela" title="Kandela – Malay" lang="ms" hreflang="ms" data-title="Kandela" 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-mn mw-list-item"><a href="https://mn.wikipedia.org/wiki/%D0%9A%D0%B0%D0%BD%D0%B4%D0%B5%D0%BB" title="Кандел – Mongolian" lang="mn" hreflang="mn" data-title="Кандел" data-language-autonym="Монгол" data-language-local-name="Mongolian" class="interlanguage-link-target"><span>Монгол</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Candela_(eenheid)" title="Candela (eenheid) – Dutch" lang="nl" hreflang="nl" data-title="Candela (eenheid)" 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%AB%E3%83%B3%E3%83%87%E3%83%A9" title="カンデラ – Japanese" lang="ja" hreflang="ja" data-title="カンデラ" 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-frr mw-list-item"><a href="https://frr.wikipedia.org/wiki/Candela" title="Candela – Northern Frisian" lang="frr" hreflang="frr" data-title="Candela" data-language-autonym="Nordfriisk" data-language-local-name="Northern Frisian" class="interlanguage-link-target"><span>Nordfriisk</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Candela" title="Candela – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Candela" 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/Candela" title="Candela – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Candela" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-oc mw-list-item"><a href="https://oc.wikipedia.org/wiki/Candela" title="Candela – Occitan" lang="oc" hreflang="oc" data-title="Candela" data-language-autonym="Occitan" data-language-local-name="Occitan" class="interlanguage-link-target"><span>Occitan</span></a></li><li class="interlanguage-link interwiki-uz mw-list-item"><a href="https://uz.wikipedia.org/wiki/Kandela" title="Kandela – Uzbek" lang="uz" hreflang="uz" data-title="Kandela" data-language-autonym="Oʻzbekcha / ўзбекча" data-language-local-name="Uzbek" class="interlanguage-link-target"><span>Oʻzbekcha / ўзбекча</span></a></li><li class="interlanguage-link interwiki-pa mw-list-item"><a href="https://pa.wikipedia.org/wiki/%E0%A8%95%E0%A9%88%E0%A8%82%E0%A8%A1%E0%A8%B2_%E0%A8%AA%E0%A8%BE%E0%A8%B5%E0%A8%B0" title="ਕੈਂਡਲ ਪਾਵਰ – Punjabi" lang="pa" hreflang="pa" data-title="ਕੈਂਡਲ ਪਾਵਰ" data-language-autonym="ਪੰਜਾਬੀ" data-language-local-name="Punjabi" class="interlanguage-link-target"><span>ਪੰਜਾਬੀ</span></a></li><li class="interlanguage-link interwiki-pnb mw-list-item"><a href="https://pnb.wikipedia.org/wiki/%D9%82%D9%86%D8%AF%DB%8C%D9%84%DB%81" title="قندیلہ – Western Punjabi" lang="pnb" hreflang="pnb" data-title="قندیلہ" data-language-autonym="پنجابی" data-language-local-name="Western Punjabi" class="interlanguage-link-target"><span>پنجابی</span></a></li><li class="interlanguage-link interwiki-pms mw-list-item"><a href="https://pms.wikipedia.org/wiki/Cand%C3%A8ila" title="Candèila – Piedmontese" lang="pms" hreflang="pms" data-title="Candèila" data-language-autonym="Piemontèis" data-language-local-name="Piedmontese" class="interlanguage-link-target"><span>Piemontèis</span></a></li><li class="interlanguage-link interwiki-nds mw-list-item"><a href="https://nds.wikipedia.org/wiki/Candela_(Eenheit)" title="Candela (Eenheit) – Low German" lang="nds" hreflang="nds" data-title="Candela (Eenheit)" data-language-autonym="Plattdüütsch" data-language-local-name="Low German" class="interlanguage-link-target"><span>Plattdüütsch</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Kandela" title="Kandela – Polish" lang="pl" hreflang="pl" data-title="Kandela" 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/Candela" title="Candela – Portuguese" lang="pt" hreflang="pt" data-title="Candela" 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/Candel%C4%83_(unitate_de_m%C4%83sur%C4%83)" title="Candelă (unitate de măsură) – Romanian" lang="ro" hreflang="ro" data-title="Candelă (unitate de măsură)" 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%B0%D0%BD%D0%B4%D0%B5%D0%BB%D0%B0" title="Кандела – Russian" lang="ru" hreflang="ru" data-title="Кандела" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-sc mw-list-item"><a href="https://sc.wikipedia.org/wiki/Candela" title="Candela – Sardinian" lang="sc" hreflang="sc" data-title="Candela" data-language-autonym="Sardu" data-language-local-name="Sardinian" class="interlanguage-link-target"><span>Sardu</span></a></li><li class="interlanguage-link interwiki-scn mw-list-item"><a href="https://scn.wikipedia.org/wiki/Cannila_(unitati_di_misura)" title="Cannila (unitati di misura) – Sicilian" lang="scn" hreflang="scn" data-title="Cannila (unitati di misura)" data-language-autonym="Sicilianu" data-language-local-name="Sicilian" class="interlanguage-link-target"><span>Sicilianu</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Candela" title="Candela – Simple English" lang="en-simple" hreflang="en-simple" data-title="Candela" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Kandela" title="Kandela – Slovak" lang="sk" hreflang="sk" data-title="Kandela" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Kandela" title="Kandela – Slovenian" lang="sl" hreflang="sl" data-title="Kandela" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-cu mw-list-item"><a href="https://cu.wikipedia.org/wiki/%D0%A1%D0%B2%D1%A3%D1%89%D0%B0_%C2%B7_%D0%BC%D1%A3%D1%80%D0%B0" title="Свѣща · мѣра – Church Slavic" lang="cu" hreflang="cu" data-title="Свѣща · мѣра" data-language-autonym="Словѣньскъ / ⰔⰎⰑⰂⰡⰐⰠⰔⰍⰟ" data-language-local-name="Church Slavic" class="interlanguage-link-target"><span>Словѣньскъ / ⰔⰎⰑⰂⰡⰐⰠⰔⰍⰟ</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/%D0%9A%D0%B0%D0%BD%D0%B4%D0%B5%D0%BB%D0%B0" title="Кандела – Serbian" lang="sr" hreflang="sr" data-title="Кандела" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/Kandela" title="Kandela – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Kandela" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Kandela" title="Kandela – Finnish" lang="fi" hreflang="fi" data-title="Kandela" 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/Candela" title="Candela – Swedish" lang="sv" hreflang="sv" data-title="Candela" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-ta mw-list-item"><a href="https://ta.wikipedia.org/wiki/%E0%AE%95%E0%AF%87%E0%AE%A3%E0%AF%8D%E0%AE%9F%E0%AF%86%E0%AE%B2%E0%AE%BE" title="கேண்டெலா – Tamil" lang="ta" hreflang="ta" data-title="கேண்டெலா" data-language-autonym="தமிழ்" data-language-local-name="Tamil" class="interlanguage-link-target"><span>தமிழ்</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B9%81%E0%B8%84%E0%B8%99%E0%B9%80%E0%B8%94%E0%B8%A5%E0%B8%B2" title="แคนเดลา – Thai" lang="th" hreflang="th" data-title="แคนเดลา" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-tg mw-list-item"><a href="https://tg.wikipedia.org/wiki/%D0%9A%D0%B0%D0%BD%D0%B4%D0%B5%D0%BB%D0%B0" title="Кандела – Tajik" lang="tg" hreflang="tg" data-title="Кандела" data-language-autonym="Тоҷикӣ" data-language-local-name="Tajik" class="interlanguage-link-target"><span>Тоҷикӣ</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Kandela" title="Kandela – Turkish" lang="tr" hreflang="tr" data-title="Kandela" 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%9A%D0%B0%D0%BD%D0%B4%D0%B5%D0%BB%D0%B0" title="Кандела – Ukrainian" lang="uk" hreflang="uk" data-title="Кандела" 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%82%D9%86%D8%AF%DB%8C%D9%84%DB%81" title="قندیلہ – Urdu" lang="ur" hreflang="ur" data-title="قندیلہ" data-language-autonym="اردو" data-language-local-name="Urdu" class="interlanguage-link-target"><span>اردو</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/Candela" title="Candela – Vietnamese" lang="vi" hreflang="vi" data-title="Candela" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-zh-classical mw-list-item"><a href="https://zh-classical.wikipedia.org/wiki/%E7%87%AD%E5%85%89" title="燭光 – Literary Chinese" lang="lzh" hreflang="lzh" data-title="燭光" data-language-autonym="文言" data-language-local-name="Literary Chinese" class="interlanguage-link-target"><span>文言</span></a></li><li class="interlanguage-link interwiki-vls mw-list-item"><a href="https://vls.wikipedia.org/wiki/Candela" title="Candela – West Flemish" lang="vls" hreflang="vls" data-title="Candela" data-language-autonym="West-Vlams" data-language-local-name="West Flemish" class="interlanguage-link-target"><span>West-Vlams</span></a></li><li class="interlanguage-link interwiki-war mw-list-item"><a href="https://war.wikipedia.org/wiki/Candela" title="Candela – Waray" lang="war" hreflang="war" data-title="Candela" data-language-autonym="Winaray" data-language-local-name="Waray" class="interlanguage-link-target"><span>Winaray</span></a></li><li class="interlanguage-link interwiki-wuu mw-list-item"><a href="https://wuu.wikipedia.org/wiki/%E5%9D%8E%E5%BE%B7%E6%8B%89" title="坎德拉 – Wu" lang="wuu" hreflang="wuu" data-title="坎德拉" data-language-autonym="吴语" data-language-local-name="Wu" class="interlanguage-link-target"><span>吴语</span></a></li><li class="interlanguage-link interwiki-zh-yue mw-list-item"><a href="https://zh-yue.wikipedia.org/wiki/%E5%9D%8E%E5%BE%B7%E6%8B%89" title="坎德拉 – Cantonese" lang="yue" hreflang="yue" data-title="坎德拉" data-language-autonym="粵語" data-language-local-name="Cantonese" class="interlanguage-link-target"><span>粵語</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E5%9D%8E%E5%BE%B7%E6%8B%89" title="坎德拉 – Chinese" lang="zh" hreflang="zh" data-title="坎德拉" data-language-autonym="中文" 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searchaux" style="display:none">SI unit of luminous intensity</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">This article is about the unit of luminous intensity. For other uses, see <a href="/wiki/Candela_(disambiguation)" class="mw-disambig" title="Candela (disambiguation)">Candela (disambiguation)</a>.</div> <p class="mw-empty-elt"> </p> <style data-mw-deduplicate="TemplateStyles:r1257001546">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent}.mw-parser-output .infobox-3cols-child{margin:auto}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme) div:not(.notheme){background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table tr{display:table-row!important}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}}</style><table class="infobox ib-unit"><tbody><tr><th colspan="2" class="infobox-above">candela</th></tr><tr><td colspan="2" class="infobox-image notheme" style="background-color: #f8f9fa;"><span typeof="mw:File"><a href="/wiki/File:Luminosity.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/e0/Luminosity.svg/290px-Luminosity.svg.png" decoding="async" width="290" height="201" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/e0/Luminosity.svg/435px-Luminosity.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/e0/Luminosity.svg/580px-Luminosity.svg.png 2x" data-file-width="672" data-file-height="465" /></a></span><div class="infobox-caption"><a href="/wiki/Photopic_vision" title="Photopic vision">Photopic</a> (black) and <a href="/wiki/Scotopic_vision" title="Scotopic vision">scotopic</a><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> (green) luminous efficiency functions. The photopic includes the CIE 1931 standard<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> (solid), the Judd–Vos 1978 modified data<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> (dashed), and the Sharpe, Stockman, Jagla & Jägle 2005 data<sup id="cite_ref-Sharpe_4-0" class="reference"><a href="#cite_note-Sharpe-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> (dotted). The horizontal axis is wavelength in nm.</div></td></tr><tr><th colspan="2" class="infobox-header">General information</th></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/System_of_units_of_measurement" title="System of units of measurement">Unit system</a></th><td class="infobox-data"><a href="/wiki/SI" class="mw-redirect" title="SI">SI</a></td></tr><tr><th scope="row" class="infobox-label">Unit of</th><td class="infobox-data"><a href="/wiki/Luminous_intensity" title="Luminous intensity">luminous intensity</a></td></tr><tr><th scope="row" class="infobox-label">Symbol</th><td class="infobox-data">cd</td></tr><tr><th colspan="2" class="infobox-header">Conversions </th></tr><tr class="nowrap"><td>1 cd <i>in ...</i></td><td><i>... is equal to ...</i></td></tr><tr style="display:none"><th colspan="2"> </th></tr><tr><th scope="row" class="infobox-label"><span class="nowrap">   </span>international candles</th><td class="infobox-data"><span class="nowrap">   </span>≈ <span class="nowrap"><span data-sort-value="7000102000000000000♠"></span>1.02</span> <a href="/wiki/Candlepower" title="Candlepower">cp</a> </td></tr><tr><th scope="row" class="infobox-label"><span class="nowrap">   </span>Hefnerkerze</th><td class="infobox-data"><span class="nowrap">   </span>≈ <span class="nowrap"><span data-sort-value="7000111000000000000♠"></span>1.11</span> <a href="/wiki/Hefner_lamp" title="Hefner lamp">HK</a> </td></tr></tbody></table><style data-mw-deduplicate="TemplateStyles:r1236303919">@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-has-images-with-white-backgrounds img{background:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-has-images-with-white-backgrounds img{background:white}}</style> <p>The <b>candela</b> (symbol: <b>cd</b>) is the unit of <a href="/wiki/Luminous_intensity" title="Luminous intensity">luminous intensity</a> in the <a href="/wiki/International_System_of_Units" title="International System of Units">International System of Units</a> (SI).<sup id="cite_ref-SIBrochure9thEd_5-0" class="reference"><a href="#cite_note-SIBrochure9thEd-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup><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> It measures luminous power per unit <a href="/wiki/Solid_angle" title="Solid angle">solid angle</a> emitted by a light source in a particular direction. Luminous intensity is analogous to <a href="/wiki/Radiant_intensity" title="Radiant intensity">radiant intensity</a>, but instead of simply adding up the contributions of every <a href="/wiki/Wavelength" title="Wavelength">wavelength</a> of light in the source's spectrum, the contribution of each wavelength is <a href="/wiki/Weighting" title="Weighting">weighted</a> by the <a href="/wiki/Luminous_efficiency_function" title="Luminous efficiency function">luminous efficiency function</a>, the model of the sensitivity of the human eye to different wavelengths, standardized by the CIE and <a href="/wiki/International_Organization_for_Standardization" title="International Organization for Standardization">ISO</a>.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Sharpe_4-1" class="reference"><a href="#cite_note-Sharpe-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup><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> A common wax <a href="/wiki/Candle" title="Candle">candle</a> emits light with a luminous intensity of roughly one candela. If emission in some directions is blocked by an opaque barrier, the emission would still be approximately one candela in the directions that are not obscured. </p><p>The word <i>candela</i> is <a href="/wiki/Latin_language" class="mw-redirect" title="Latin language">Latin</a> for <i>candle</i>. The old name "candle" is still sometimes used, as in <i><a href="/wiki/Foot-candle" title="Foot-candle">foot-candle</a></i> and the modern definition of <i><a href="/wiki/Candlepower" title="Candlepower">candlepower</a></i>.<sup id="cite_ref-Webster_9-0" class="reference"><a href="#cite_note-Webster-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Definition">Definition</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Candela&action=edit&section=1" title="Edit section: Definition"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The 26th <a href="/wiki/General_Conference_on_Weights_and_Measures" title="General Conference on Weights and Measures">General Conference on Weights and Measures</a> (CGPM) redefined the candela in 2018.<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><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> The new definition, which took effect on 20 May 2019, is: </p> <blockquote><p>The candela [...] is defined by taking the fixed numerical value of the <a href="/wiki/Luminous_efficacy" title="Luminous efficacy">luminous efficacy</a> of monochromatic radiation of frequency <span class="nowrap"><span data-sort-value="7014540000000000000♠"></span>540<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>12</sup> Hz</span>,<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>a<span class="cite-bracket">]</span></a></sup> <i>K</i><sub>cd</sub>, to be 683 when expressed in the unit lm W<sup>−1</sup>, which is equal to <span class="nowrap">cd sr W<sup>−1</sup></span>, or <span class="nowrap">cd sr kg<sup>−1</sup> m<sup>−2</sup> s<sup>3</sup></span>, where the kilogram, metre and second are defined in terms of <i><a href="/wiki/Planck_constant" title="Planck constant">h</a></i>, <i><a href="/wiki/Speed_of_light_in_vacuum" class="mw-redirect" title="Speed of light in vacuum">c</a></i> and <a href="/wiki/Unperturbed_ground_state_hyperfine_transition_frequency_of_the_caesium_133_atom" class="mw-redirect" title="Unperturbed ground state hyperfine transition frequency of the caesium 133 atom">Δ<i>ν</i><sub>Cs</sub></a>.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup></p></blockquote> <div class="mw-heading mw-heading3"><h3 id="Explanation">Explanation</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Candela&action=edit&section=2" title="Edit section: Explanation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Linear_visible_spectrum.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/d/d9/Linear_visible_spectrum.svg/330px-Linear_visible_spectrum.svg.png" decoding="async" width="330" height="63" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/d9/Linear_visible_spectrum.svg/495px-Linear_visible_spectrum.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/d9/Linear_visible_spectrum.svg/660px-Linear_visible_spectrum.svg.png 2x" data-file-width="605" data-file-height="115" /></a><figcaption></figcaption></figure> <p>The frequency chosen is in the <a href="/wiki/Visible_light" class="mw-redirect" title="Visible light">visible spectrum</a> near <a href="/wiki/Green" title="Green">green</a>, corresponding to a wavelength of about 555 nanometres. The <a href="/wiki/Human_eye" title="Human eye">human eye</a>, when <a href="/wiki/Adaptation_(eye)" title="Adaptation (eye)">adapted</a> for bright conditions, is most sensitive near this frequency. Under these conditions, <a href="/wiki/Photopic_vision" title="Photopic vision">photopic vision</a> dominates the visual perception of our eyes over the <a href="/wiki/Scotopic_vision" title="Scotopic vision">scotopic vision</a>. At other frequencies, more radiant intensity is required to achieve the same luminous intensity, according to the frequency response of the human eye. The luminous intensity for light of a particular wavelength <i>λ</i> is given by <span class="mwe-math-element"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle I_{\mathrm {v} }(\lambda )=683.002\ \mathrm {lm/W} \cdot {\overline {y}}(\lambda )\cdot I_{\mathrm {e} }(\lambda ),}"> <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">v</mi> </mrow> </mrow> </msub> <mo stretchy="false">(</mo> <mi>λ</mi> <mo stretchy="false">)</mo> <mo>=</mo> <mn>683.002</mn> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">l</mi> <mi mathvariant="normal">m</mi> <mrow class="MJX-TeXAtom-ORD"> <mo>/</mo> </mrow> <mi mathvariant="normal">W</mi> </mrow> <mo>⋅</mo> <mrow class="MJX-TeXAtom-ORD"> <mover> <mi>y</mi> <mo accent="false">¯</mo> </mover> </mrow> <mo stretchy="false">(</mo> <mi>λ</mi> <mo stretchy="false">)</mo> <mo>⋅</mo> <msub> <mi>I</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">e</mi> </mrow> </mrow> </msub> <mo stretchy="false">(</mo> <mi>λ</mi> <mo stretchy="false">)</mo> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle I_{\mathrm {v} }(\lambda )=683.002\ \mathrm {lm/W} \cdot {\overline {y}}(\lambda )\cdot I_{\mathrm {e} }(\lambda ),}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/f10f21c61c8744adbeed4d6d259332e1bd38ec11" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:36.323ex; height:2.843ex;" alt="{\displaystyle I_{\mathrm {v} }(\lambda )=683.002\ \mathrm {lm/W} \cdot {\overline {y}}(\lambda )\cdot I_{\mathrm {e} }(\lambda ),}"></span> where <span class="texhtml"><i>I</i><sub>v</sub>(<i>λ</i>)</span> is the <a href="/wiki/Luminous_intensity" title="Luminous intensity">luminous intensity</a>, <span class="texhtml"><i>I</i><sub>e</sub>(<i>λ</i>)</span> is the <a href="/wiki/Radiant_intensity" title="Radiant intensity">radiant intensity</a> 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="{\textstyle \textstyle {\overline {y}}(\lambda )}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <mstyle displaystyle="false" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mover> <mi>y</mi> <mo accent="false">¯</mo> </mover> </mrow> <mo stretchy="false">(</mo> <mi>λ</mi> <mo stretchy="false">)</mo> </mstyle> </mstyle> </mrow> <annotation encoding="application/x-tex">{\textstyle \textstyle {\overline {y}}(\lambda )}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3b2e8b3d8b5fa0b5c1add7177a5dc9e09c226d7a" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:4.446ex; height:2.843ex;" alt="{\textstyle \textstyle {\overline {y}}(\lambda )}"></span> is the <a href="/wiki/Photopic" class="mw-redirect" title="Photopic">photopic</a> <a href="/wiki/Luminous_efficiency_function" title="Luminous efficiency function">luminous efficiency function</a>. If more than one wavelength is present (as is usually the case), one must integrate over the <a href="/wiki/Spectrum" title="Spectrum">spectrum</a> of wavelengths to get the total luminous intensity. </p> <div class="mw-heading mw-heading3"><h3 id="Examples">Examples</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Candela&action=edit&section=3" title="Edit section: Examples"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>A common candle emits light with roughly 1 cd luminous intensity.</li> <li>A 25 W <a href="/wiki/Compact_fluorescent_light_bulb" class="mw-redirect" title="Compact fluorescent light bulb">compact fluorescent light bulb</a> puts out around 1700 <a href="/wiki/Lumen_(unit)" title="Lumen (unit)">lumens</a>; if that light is radiated equally in all directions (i.e. over 4<span class="texhtml mvar" style="font-style:italic;">π</span> <a href="/wiki/Steradian" title="Steradian">steradians</a>), it will have an intensity 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 I_{\text{V}}={\frac {1700\ {\text{lm}}}{4\pi \ {\text{sr}}}}\approx 135\ {\text{lm}}/{\text{sr}}=135\ {\text{cd}}.}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>I</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>V</mtext> </mrow> </msub> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>1700</mn> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mtext>lm</mtext> </mrow> </mrow> <mrow> <mn>4</mn> <mi>π</mi> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mtext>sr</mtext> </mrow> </mrow> </mfrac> </mrow> <mo>≈</mo> <mn>135</mn> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mtext>lm</mtext> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mo>/</mo> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mtext>sr</mtext> </mrow> <mo>=</mo> <mn>135</mn> <mtext> </mtext> <mrow class="MJX-TeXAtom-ORD"> <mtext>cd</mtext> </mrow> <mo>.</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle I_{\text{V}}={\frac {1700\ {\text{lm}}}{4\pi \ {\text{sr}}}}\approx 135\ {\text{lm}}/{\text{sr}}=135\ {\text{cd}}.}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/30277d8b6a69ad7c80896a800c3be85aca95ad50" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:37.113ex; height:5.343ex;" alt="{\displaystyle I_{\text{V}}={\frac {1700\ {\text{lm}}}{4\pi \ {\text{sr}}}}\approx 135\ {\text{lm}}/{\text{sr}}=135\ {\text{cd}}.}"></span></li> <li>Focused into a 20° beam (0.095 steradians), the same light bulb would have an intensity of around 18,000 cd or 18 kcd within the beam.</li></ul> <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=Candela&action=edit&section=4" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Prior to 1948, various standards for luminous intensity were in use in a number of countries. These were typically based on the brightness of the flame from a "standard candle" of defined composition, or the brightness of an incandescent filament of specific design. One of the best-known of these was the English standard of candlepower. One candlepower was the light produced by a pure <a href="/wiki/Spermaceti" title="Spermaceti">spermaceti</a> candle weighing one sixth of a pound and burning at a rate of 120 <a href="/wiki/Grain_(unit)" title="Grain (unit)">grains</a> per hour. Germany, Austria and Scandinavia used the <a href="/wiki/Hefnerkerze" class="mw-redirect" title="Hefnerkerze">Hefnerkerze</a>, a unit based on the output of a <a href="/wiki/Hefner_lamp" title="Hefner lamp">Hefner lamp</a>.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p><p>A better standard for luminous intensity was needed. In 1884, <a href="/wiki/Jules_Violle" title="Jules Violle">Jules Violle</a> had proposed a standard based on the light emitted by 1 cm<sup>2</sup> of <a href="/wiki/Platinum" title="Platinum">platinum</a> at its melting point (or freezing point). The resulting unit of intensity, called the "violle", was roughly equal to 60 English candlepower. Platinum was convenient for this purpose because it had a high enough melting point, was not prone to <a href="/wiki/Oxidation" class="mw-redirect" title="Oxidation">oxidation</a>, and could be obtained in pure form.<sup id="cite_ref-Cottington_15-0" class="reference"><a href="#cite_note-Cottington-15"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> Violle showed that the intensity emitted by pure platinum was strictly dependent on its temperature, and so platinum at its melting point should have a consistent luminous intensity. </p><p>In practice, realizing a standard based on Violle's proposal turned out to be more difficult than expected.<sup id="cite_ref-Cottington_15-1" class="reference"><a href="#cite_note-Cottington-15"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> Impurities on the surface of the platinum could directly affect its emissivity, and in addition impurities could affect the luminous intensity by altering the melting point. Over the following half century various scientists tried to make a practical intensity standard based on incandescent platinum. The successful approach was to suspend a hollow shell of <a href="/wiki/Thorium_dioxide" title="Thorium dioxide">thorium dioxide</a> with a small hole in it in a bath of molten platinum. The shell (cavity) serves as a <a href="/wiki/Black_body" title="Black body">black body</a>, producing <a href="/wiki/Black-body_radiation" title="Black-body radiation">black-body radiation</a> that depends on the temperature and is not sensitive to details of how the device is constructed. </p><p>In 1937, the <i><a href="/wiki/Commission_Internationale_de_l%27%C3%89clairage" class="mw-redirect" title="Commission Internationale de l'Éclairage">Commission Internationale de l'Éclairage</a></i> (International Commission on Illumination) and the CIPM proposed a "new candle" based on this concept, with value chosen to make it similar to the earlier unit candlepower. The decision was promulgated by the CIPM in 1946: </p> <blockquote><p>The value of the <b>new candle</b> is such that the brightness of the full radiator at the temperature of solidification of platinum is 60 new candles per <a href="/wiki/Square_centimetre" class="mw-redirect" title="Square centimetre">square centimetre</a>.<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup></p></blockquote> <p>It was then ratified in 1948 by the 9th CGPM<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> which adopted a new name for this unit, the <i>candela</i>. In 1967 the 13th CGPM removed the term "new candle" and gave an amended version of the candela definition, specifying the atmospheric pressure applied to the freezing platinum: </p> <blockquote><p>The candela is the luminous intensity, in the perpendicular direction, of a surface of <span class="nowrap">1 / 600 000</span> square metre of a black body at the temperature of freezing platinum under a pressure of <span class="nowrap">101 325</span> newtons per square metre.<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup></p></blockquote> <p>In 1979, because of the difficulties in realizing a Planck radiator at high temperatures and the new possibilities offered by <a href="/wiki/Radiometry" title="Radiometry">radiometry</a>, the 16th CGPM adopted a new definition of the candela:<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> </p> <blockquote> <p>The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency <span class="nowrap"><span data-sort-value="7014540000000000000♠"></span>540<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>12</sup> <a href="/wiki/Hertz" title="Hertz">hertz</a></span> and that has a <a href="/wiki/Radiant_intensity" title="Radiant intensity">radiant intensity</a> in that direction of <style data-mw-deduplicate="TemplateStyles:r1214402035">.mw-parser-output .sfrac{white-space:nowrap}.mw-parser-output .sfrac.tion,.mw-parser-output .sfrac .tion{display:inline-block;vertical-align:-0.5em;font-size:85%;text-align:center}.mw-parser-output .sfrac .num{display:block;line-height:1em;margin:0.0em 0.1em;border-bottom:1px solid}.mw-parser-output .sfrac .den{display:block;line-height:1em;margin:0.1em 0.1em}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">683</span></span>⁠</span> <a href="/wiki/Watt" title="Watt">watt</a> per <a href="/wiki/Steradian" title="Steradian">steradian</a>. </p> </blockquote> <p>The definition describes how to produce a light source that (by definition) emits one candela, but does not specify the luminous efficiency function for weighting radiation at other frequencies. Such a source could then be used to calibrate instruments designed to measure luminous intensity with reference to a specified luminous efficiency function. An appendix to the SI Brochure<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> makes it clear that the luminous efficiency function is not uniquely specified, but must be selected to fully define the candela. </p><p>The arbitrary (1/683) term was chosen so that the new definition would precisely match the old definition. Although the candela is now defined in terms of the <a href="/wiki/Second" title="Second">second</a> (an SI base unit) and the watt (a derived SI unit), the candela remains a base unit of the SI system, by definition.<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> </p><p>The 26th CGPM approved the modern definition of the candela in 2018 as part of the <a href="/wiki/2019_revision_of_the_SI" title="2019 revision of the SI">2019 revision of the SI</a>, which redefined the SI base units in terms of fundamental physical constants. </p> <div class="mw-heading mw-heading2"><h2 id="SI_photometric_light_units">SI photometric light units</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Candela&action=edit&section=5" title="Edit section: SI photometric light units"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><span class="anchor" id="table-si-photometry-units"></span> </p> <table class="wikitable plainrowheaders"> <caption><style data-mw-deduplicate="TemplateStyles:r1045256916">.mw-parser-output .navbar-header{text-align:center;position:relative;white-space:nowrap}.mw-parser-output .navbar-header .navbar{position:absolute;right:0;top:0;margin:0 5px}</style><div class="navbar-header"><span style="font-size:130%;">SI photometry quantities</span><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:": "}.mw-parser-output .hlist dd::after,.mw-parser-output .hlist li::after{content:" · ";font-weight:bold}.mw-parser-output .hlist dd:last-child::after,.mw-parser-output .hlist dt:last-child::after,.mw-parser-output .hlist li:last-child::after{content:none}.mw-parser-output .hlist dd dd:first-child::before,.mw-parser-output .hlist dd dt:first-child::before,.mw-parser-output .hlist dd li:first-child::before,.mw-parser-output .hlist dt dd:first-child::before,.mw-parser-output .hlist dt dt:first-child::before,.mw-parser-output .hlist dt li:first-child::before,.mw-parser-output .hlist li dd:first-child::before,.mw-parser-output .hlist li dt:first-child::before,.mw-parser-output .hlist li li:first-child::before{content:" (";font-weight:normal}.mw-parser-output .hlist dd dd:last-child::after,.mw-parser-output .hlist dd dt:last-child::after,.mw-parser-output .hlist dd li:last-child::after,.mw-parser-output .hlist dt dd:last-child::after,.mw-parser-output .hlist dt dt:last-child::after,.mw-parser-output .hlist dt li:last-child::after,.mw-parser-output .hlist li dd:last-child::after,.mw-parser-output .hlist li dt:last-child::after,.mw-parser-output .hlist li li:last-child::after{content:")";font-weight:normal}.mw-parser-output .hlist ol{counter-reset:listitem}.mw-parser-output .hlist ol>li{counter-increment:listitem}.mw-parser-output .hlist ol>li::before{content:" "counter(listitem)"\a0 "}.mw-parser-output .hlist dd ol>li:first-child::before,.mw-parser-output .hlist dt ol>li:first-child::before,.mw-parser-output .hlist li ol>li:first-child::before{content:" ("counter(listitem)"\a0 "}</style><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:SI_light_units" title="Template:SI light units"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:SI_light_units" title="Template talk:SI light units"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:SI_light_units" title="Special:EditPage/Template:SI light units"><abbr title="Edit this template">e</abbr></a></li></ul></div></div> </caption> <tbody><tr> <th scope="col" colspan="2">Quantity </th> <th scope="col" colspan="2">Unit </th> <th scope="col" rowspan="2">Dimension<br /><sup id="cite_ref-note-dimension-symbol_23-0" class="reference"><a href="#cite_note-note-dimension-symbol-23"><span class="cite-bracket">[</span>nb 1<span class="cite-bracket">]</span></a></sup> </th> <th scope="col" rowspan="2">Notes </th></tr> <tr> <th scope="col">Name </th> <th scope="col">Symbol<sup id="cite_ref-note-suffix-v_24-0" class="reference"><a href="#cite_note-note-suffix-v-24"><span class="cite-bracket">[</span>nb 2<span class="cite-bracket">]</span></a></sup> </th> <th scope="col">Name </th> <th scope="col">Symbol </th></tr> <tr> <th scope="row"><a href="/wiki/Luminous_energy" title="Luminous energy">Luminous energy</a> </th> <td><span class="texhtml"><i>Q</i><sub>v</sub></span><sup id="cite_ref-note-alternative-symbol-photometric_25-0" class="reference"><a href="#cite_note-note-alternative-symbol-photometric-25"><span class="cite-bracket">[</span>nb 3<span class="cite-bracket">]</span></a></sup> </td> <td><a href="/wiki/Lumen_second" title="Lumen second">lumen second</a> </td> <td><a href="/wiki/Lumen_(unit)" title="Lumen (unit)">lm</a>⋅s </td> <td><b>T</b>⋅<b>J</b> </td> <td>The lumen second is sometimes called the <i>talbot</i>. </td></tr> <tr> <th scope="row"><a href="/wiki/Luminous_flux" title="Luminous flux">Luminous flux</a>, luminous power </th> <td><span class="texhtml">Φ<sub><a href="/wiki/Luminosity_function" class="mw-redirect" title="Luminosity function">v</a></sub></span><sup id="cite_ref-note-alternative-symbol-photometric_25-1" class="reference"><a href="#cite_note-note-alternative-symbol-photometric-25"><span class="cite-bracket">[</span>nb 3<span class="cite-bracket">]</span></a></sup> </td> <td><a href="/wiki/Lumen_(unit)" title="Lumen (unit)">lumen</a> (= candela <a href="/wiki/Steradian" title="Steradian">steradian</a>) </td> <td>lm (= cd⋅sr) </td> <td><b>J</b> </td> <td>Luminous energy per unit time </td></tr> <tr> <th scope="row"><a href="/wiki/Luminous_intensity" title="Luminous intensity">Luminous intensity</a> </th> <td><span class="texhtml"><i>I</i><sub>v</sub></span> </td> <td><a class="mw-selflink selflink">candela</a> (= lumen per steradian) </td> <td><a class="mw-selflink selflink">cd</a> (= lm/sr) </td> <td><b>J</b> </td> <td>Luminous flux per unit <a href="/wiki/Solid_angle" title="Solid angle">solid angle</a> </td></tr> <tr> <th scope="row"><a href="/wiki/Luminance" title="Luminance">Luminance</a> </th> <td><span class="texhtml"><i>L</i><sub>v</sub></span> </td> <td><a href="/wiki/Candela_per_square_metre" title="Candela per square metre">candela per square metre</a> </td> <td>cd/m<sup>2</sup> (= lm/(sr⋅m<sup>2</sup>)) </td> <td><b>L</b><sup>−2</sup>⋅<b>J</b> </td> <td>Luminous flux per unit solid angle per unit <i>projected</i> source area. The candela per square metre is sometimes called the <i><a href="/wiki/Nit_(unit)" class="mw-redirect" title="Nit (unit)">nit</a></i>. </td></tr> <tr> <th scope="row"><a href="/wiki/Illuminance" title="Illuminance">Illuminance</a> </th> <td><span class="texhtml"><i>E</i><sub>v</sub></span> </td> <td><a href="/wiki/Lux" title="Lux">lux</a> (= lumen per square metre) </td> <td><a href="/wiki/Lux" title="Lux">lx</a> (= lm/m<sup>2</sup>) </td> <td><b>L</b><sup>−2</sup>⋅<b>J</b> </td> <td>Luminous flux <i>incident</i> on a surface </td></tr> <tr> <th scope="row"><a href="/wiki/Luminous_exitance" class="mw-redirect" title="Luminous exitance">Luminous exitance</a>, luminous emittance </th> <td><span class="texhtml"><i>M</i><sub>v</sub></span> </td> <td>lumen per square metre </td> <td>lm/m<sup>2</sup> </td> <td><b>L</b><sup>−2</sup>⋅<b>J</b> </td> <td>Luminous flux <i>emitted</i> from a surface </td></tr> <tr> <th scope="row"><a href="/wiki/Luminous_exposure" class="mw-redirect" title="Luminous exposure">Luminous exposure</a> </th> <td><span class="texhtml"><i>H</i><sub>v</sub></span> </td> <td><a href="/wiki/Lux_second" class="mw-redirect" title="Lux second">lux second</a> </td> <td>lx⋅s </td> <td><b>L</b><sup>−2</sup>⋅<b>T</b>⋅<b>J</b> </td> <td>Time-integrated illuminance </td></tr> <tr> <th scope="row">Luminous energy density </th> <td><span class="texhtml"><i>ω</i><sub>v</sub></span> </td> <td>lumen second per cubic metre </td> <td>lm⋅s/m<sup>3</sup> </td> <td><b>L</b><sup>−3</sup>⋅<b>T</b>⋅<b>J</b> </td> <td> </td></tr> <tr> <th scope="row"><a href="/wiki/Luminous_efficacy" title="Luminous efficacy">Luminous efficacy</a> (of radiation) </th> <td><span class="texhtml"><i>K</i></span> </td> <td>lumen per <a href="/wiki/Watt" title="Watt">watt</a> </td> <td>lm/<a href="/wiki/Watt" title="Watt">W</a> </td> <td><b>M</b><sup>−1</sup>⋅<b>L</b><sup>−2</sup>⋅<b>T</b><sup>3</sup>⋅<b>J</b> </td> <td>Ratio of luminous flux to <a href="/wiki/Radiant_flux" title="Radiant flux">radiant flux</a> </td></tr> <tr> <th scope="row"><a href="/wiki/Luminous_efficacy" title="Luminous efficacy">Luminous efficacy</a> (of a source) </th> <td><span class="texhtml mvar" style="font-style:italic;">η</span><sup id="cite_ref-note-alternative-symbol-photometric_25-2" class="reference"><a href="#cite_note-note-alternative-symbol-photometric-25"><span class="cite-bracket">[</span>nb 3<span class="cite-bracket">]</span></a></sup> </td> <td>lumen per <a href="/wiki/Watt" title="Watt">watt</a> </td> <td>lm/<a href="/wiki/Watt" title="Watt">W</a> </td> <td><b>M</b><sup>−1</sup>⋅<b>L</b><sup>−2</sup>⋅<b>T</b><sup>3</sup>⋅<b>J</b> </td> <td>Ratio of luminous flux to power consumption </td></tr> <tr> <th scope="row"><a href="/wiki/Luminous_efficiency" class="mw-redirect" title="Luminous efficiency">Luminous efficiency</a>, luminous coefficient </th> <td><span class="texhtml mvar" style="font-style:italic;">V</span> </td> <td> </td> <td> </td> <td><b>1</b> </td> <td>Luminous efficacy normalized by the maximum possible efficacy </td></tr> <tr> <td style="text-align:center;" colspan="6">See also: <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><div class="hlist inline"><ul><li><a href="/wiki/SI" class="mw-redirect" title="SI">SI</a></li><li><a href="/wiki/Photometry_(optics)" title="Photometry (optics)">Photometry</a></li><li><a href="/wiki/Radiometry" title="Radiometry">Radiometry</a></li></ul></div> </td></tr></tbody></table><style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-note-dimension-symbol-23"><span class="mw-cite-backlink"><b><a href="#cite_ref-note-dimension-symbol_23-0">^</a></b></span> <span class="reference-text">The symbols in this column denote <a href="/wiki/Dimensional_analysis#Definition" title="Dimensional analysis">dimensions</a>; "<b>L</b>", "<b>T</b>" and "<b>J</b>" are for length, time and luminous intensity respectively, not the symbols for the <a href="/wiki/Unit_of_measurement" title="Unit of measurement">units</a> litre, tesla and joule.</span> </li> <li id="cite_note-note-suffix-v-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-note-suffix-v_24-0">^</a></b></span> <span class="reference-text"><a href="/wiki/Standards_organization" title="Standards organization">Standards organizations</a> recommend that photometric quantities be denoted with a subscript "v" (for "visual") to avoid confusion with radiometric or <a href="/wiki/Photon" title="Photon">photon</a> quantities. For example: <i>USA Standard Letter Symbols for Illuminating Engineering</i> USAS Z7.1-1967, Y10.18-1967</span> </li> <li id="cite_note-note-alternative-symbol-photometric-25"><span class="mw-cite-backlink">^ <a href="#cite_ref-note-alternative-symbol-photometric_25-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-note-alternative-symbol-photometric_25-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-note-alternative-symbol-photometric_25-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text">Alternative symbols sometimes seen: <span class="texhtml mvar" style="font-style:italic;">W</span> for luminous energy, <span class="texhtml mvar" style="font-style:italic;">P</span> or <span class="texhtml mvar" style="font-style:italic;">F</span> for luminous flux, and <span class="texhtml mvar" style="font-style:italic;">ρ</span> for luminous efficacy of a source.</span> </li> </ol></div></div> <div class="mw-heading mw-heading3"><h3 id="Relationships_between_luminous_intensity,_luminous_flux,_and_illuminance"><span id="Relationships_between_luminous_intensity.2C_luminous_flux.2C_and_illuminance"></span>Relationships between luminous intensity, luminous flux, and illuminance</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Candela&action=edit&section=6" title="Edit section: Relationships between luminous intensity, luminous flux, and illuminance"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>If a source emits a known luminous intensity <span class="texhtml"><i>I</i><sub>v</sub></span> (in candelas) in a well-defined cone, the total <a href="/wiki/Luminous_flux" title="Luminous flux">luminous flux</a> <span class="texhtml"><i>Φ</i><sub>v</sub></span> in <a href="/wiki/Lumen_(unit)" title="Lumen (unit)">lumens</a> is given by <span class="mwe-math-element"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \Phi _{\mathrm {v} }=I_{\mathrm {v} }2\pi [1-\cos(A/2)]}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi mathvariant="normal">Φ</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">v</mi> </mrow> </mrow> </msub> <mo>=</mo> <msub> <mi>I</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">v</mi> </mrow> </mrow> </msub> <mn>2</mn> <mi>π</mi> <mo stretchy="false">[</mo> <mn>1</mn> <mo>−</mo> <mi>cos</mi> <mo>⁡</mo> <mo stretchy="false">(</mo> <mi>A</mi> <mrow class="MJX-TeXAtom-ORD"> <mo>/</mo> </mrow> <mn>2</mn> <mo stretchy="false">)</mo> <mo stretchy="false">]</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \Phi _{\mathrm {v} }=I_{\mathrm {v} }2\pi [1-\cos(A/2)]}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d847e08c659cc946e07e4dc212c8b9b8d8a2ef5b" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:24.779ex; height:2.843ex;" alt="{\displaystyle \Phi _{\mathrm {v} }=I_{\mathrm {v} }2\pi [1-\cos(A/2)]}"></span> where <span class="texhtml"><i>A</i></span> is the <i>radiation angle</i> of the lamp—the full vertex angle of the emission cone. For example, a lamp that emits 590 cd with a radiation angle of 40° emits about 224 lumens. See <a href="/wiki/MR16" class="mw-redirect" title="MR16">MR16</a> for emission angles of some common lamps. </p><p>If the source emits light uniformly in all directions, the flux can be found by multiplying the intensity by 4<span class="texhtml mvar" style="font-style:italic;">π</span>: a uniform 1 candela source emits 4<span class="texhtml mvar" style="font-style:italic;">π</span> lumens (approximately 12.566 lumens). </p><p>For the purpose of measuring illumination, the candela is not a practical unit, as it only applies to idealized point light sources, each approximated by a source small compared to the distance from which its luminous radiation is measured, also assuming that it is done so in the absence of other light sources. What gets directly measured by a <a href="/wiki/Light_meter" title="Light meter">light meter</a> is incident light on a sensor of finite area, i.e. <a href="/wiki/Illuminance" title="Illuminance">illuminance</a> in lm/m<sup>2</sup> (lux). However, if designing illumination from many point light sources, like light bulbs, of known approximate omnidirectionally uniform intensities, the contributions to illuminance from <a href="/wiki/Incoherent_light" class="mw-redirect" title="Incoherent light">incoherent light</a> being additive, it is mathematically estimated as follows. If <span class="texhtml"><b>r</b><sub><i>i</i></sub></span> is the position of the <i>i</i>th source of uniform intensity <span class="texhtml"><i>I<sub>i</sub></i></span>, and <span class="texhtml"><b>â</b></span> is the unit vector <a href="/wiki/Normal_(geometry)" title="Normal (geometry)">normal</a> to the illuminated elemental opaque area <span class="texhtml"><i>dA</i></span> being measured, and provided that all light sources lie in the same half-space divided by the plane of this area, <span class="mwe-math-element"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\text{illuminance at point }}\mathbf {r} {\text{ on }}dA{\text{, }}E_{\mathrm {v} }(\mathbf {r} )=\sum _{i}{{\frac {|\mathbf {\hat {a}} \cdot (\mathbf {r} -\mathbf {r} _{i})|}{|\mathbf {r} -\mathbf {r} _{i}|^{3}}}I_{i}}.}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mtext>illuminance at point </mtext> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">r</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mtext> on </mtext> </mrow> <mi>d</mi> <mi>A</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>, </mtext> </mrow> <msub> <mi>E</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">v</mi> </mrow> </mrow> </msub> <mo stretchy="false">(</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">r</mi> </mrow> <mo stretchy="false">)</mo> <mo>=</mo> <munder> <mo>∑</mo> <mrow class="MJX-TeXAtom-ORD"> <mi>i</mi> </mrow> </munder> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">|</mo> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mover> <mi mathvariant="bold">a</mi> <mo mathvariant="bold" stretchy="false">^</mo> </mover> </mrow> </mrow> <mo>⋅</mo> <mo stretchy="false">(</mo> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">r</mi> </mrow> <mo>−</mo> <msub> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">r</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mi>i</mi> </mrow> </msub> <mo stretchy="false">)</mo> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">|</mo> </mrow> </mrow> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">|</mo> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">r</mi> </mrow> <mo>−</mo> <msub> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">r</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mi>i</mi> </mrow> </msub> <msup> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">|</mo> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> </msup> </mrow> </mfrac> </mrow> <msub> <mi>I</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>i</mi> </mrow> </msub> </mrow> <mo>.</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\text{illuminance at point }}\mathbf {r} {\text{ on }}dA{\text{, }}E_{\mathrm {v} }(\mathbf {r} )=\sum _{i}{{\frac {|\mathbf {\hat {a}} \cdot (\mathbf {r} -\mathbf {r} _{i})|}{|\mathbf {r} -\mathbf {r} _{i}|^{3}}}I_{i}}.}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/6a6fe5f7614d199a9215ff0ec0a9aed9b09f09ec" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -3.005ex; width:57.477ex; height:6.843ex;" alt="{\displaystyle {\text{illuminance at point }}\mathbf {r} {\text{ on }}dA{\text{, }}E_{\mathrm {v} }(\mathbf {r} )=\sum _{i}{{\frac {|\mathbf {\hat {a}} \cdot (\mathbf {r} -\mathbf {r} _{i})|}{|\mathbf {r} -\mathbf {r} _{i}|^{3}}}I_{i}}.}"></span> In the case of a single point light source of intensity <i>I<sub>v</sub></i>, at a distance <i>r</i> and normally incident, this reduces to <span class="mwe-math-element"><span class="mwe-math-mathml-display mwe-math-mathml-a11y" style="display: none;"><math display="block" xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle E_{\mathrm {v} }(r)={\frac {I_{\mathrm {v} }}{r^{2}}}.}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>E</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">v</mi> </mrow> </mrow> </msub> <mo stretchy="false">(</mo> <mi>r</mi> <mo stretchy="false">)</mo> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <msub> <mi>I</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">v</mi> </mrow> </mrow> </msub> <msup> <mi>r</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> </mfrac> </mrow> <mo>.</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle E_{\mathrm {v} }(r)={\frac {I_{\mathrm {v} }}{r^{2}}}.}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0cae26f033fcc7a6089364431af7d15bf144a843" class="mwe-math-fallback-image-display mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.171ex; width:12.378ex; height:5.509ex;" alt="{\displaystyle E_{\mathrm {v} }(r)={\frac {I_{\mathrm {v} }}{r^{2}}}.}"></span> </p> <div class="mw-heading mw-heading2"><h2 id="SI_multiples">SI multiples</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Candela&action=edit&section=7" title="Edit section: SI multiples"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Like other SI units, the candela can also be modified by adding a <a href="/wiki/Metric_prefix" title="Metric prefix">metric prefix</a> that multiplies it by a <a href="/wiki/Power_of_10" title="Power of 10">power of 10</a>, for example millicandela (mcd) for 10<sup>−3</sup> candela. </p> <div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Candela&action=edit&section=8" title="Edit section: Notes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239543626"><div class="reflist reflist-lower-alpha"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text">This frequency corresponds to a <a href="/wiki/Wavelength" title="Wavelength">wavelength</a> of 555 nm in air, which is yellowish-green light approximately at the peak of human visual response. The color can be approximated on an <a href="/wiki/SRGB" title="SRGB">sRGB</a> display with <a href="/wiki/CSS" title="CSS">CSS</a> color value <code>rgb(120,255,0)</code> or hex <code>#78ff00</code> <span style="display:inline-block;border:1.62px solid #55b900;vertical-align:text-top;" title="#78ff00"><span class="mw-no-invert" style="display:block;padding:0;width:1em;height:1em;background:#78ff00;color:inherit;"> </span></span>. </span> </li> </ol></div></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=Candela&action=edit&section=9" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239543626"><div class="reflist reflist-columns references-column-width" style="column-width: 30em;"> <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 .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="http://www.cvrl.org/database/text/lum/scvl.htm">"CIE Scotopic luminosity curve (1951)"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=CIE+Scotopic+luminosity+curve+%281951%29&rft_id=http%3A%2F%2Fwww.cvrl.org%2Fdatabase%2Ftext%2Flum%2Fscvl.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACandela" class="Z3988"></span></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.cvrl.org/database/text/cmfs/ciexyz31.htm">"CIE (1931) 2-deg color matching functions"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=CIE+%281931%29+2-deg+color+matching+functions&rft_id=http%3A%2F%2Fwww.cvrl.org%2Fdatabase%2Ftext%2Fcmfs%2Fciexyz31.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACandela" class="Z3988"></span></span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</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="http://www.cvrl.org/database/text/lum/vljv.htm">"Judd–Vos modified CIE 2-deg photopic luminosity curve (1978)"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Judd%E2%80%93Vos+modified+CIE+2-deg+photopic+luminosity+curve+%281978%29&rft_id=http%3A%2F%2Fwww.cvrl.org%2Fdatabase%2Ftext%2Flum%2Fvljv.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACandela" class="Z3988"></span></span> </li> <li id="cite_note-Sharpe-4"><span class="mw-cite-backlink">^ <a href="#cite_ref-Sharpe_4-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Sharpe_4-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.cvrl.org/database/text/lum/ssvl2.htm">Sharpe, Stockman, Jagla & Jägle (2005) 2-deg V*(l) luminous efficiency function</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20070927222337/http://www.cvrl.org/database/text/lum/ssvl2.htm">Archived</a> 27 September 2007 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a></span> </li> <li id="cite_note-SIBrochure9thEd-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-SIBrochure9thEd_5-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFInternational_Bureau_of_Weights_and_Measures2019" class="citation cs2"><a href="/wiki/New_SI" class="mw-redirect" title="New SI">International Bureau of Weights and Measures</a> (20 May 2019), <a rel="nofollow" class="external text" href="https://www.bipm.org/utils/common/pdf/si-brochure/SI-Brochure-9.pdf"><i>The International System of Units (SI)</i></a> <span class="cs1-format">(PDF)</span> (9th ed.), <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-92-822-2272-0" title="Special:BookSources/978-92-822-2272-0"><bdi>978-92-822-2272-0</bdi></a>, <a rel="nofollow" class="external text" href="https://web.archive.org/web/20211018184555/https://www.bipm.org/documents/20126/41483022/SI-Brochure-9.pdf/fcf090b2-04e6-88cc-1149-c3e029ad8232">archived</a> from the original on 18 October 2021</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+International+System+of+Units+%28SI%29&rft.edition=9th&rft.date=2019-05-20&rft.isbn=978-92-822-2272-0&rft.au=International+Bureau+of+Weights+and+Measures&rft_id=https%3A%2F%2Fwww.bipm.org%2Futils%2Fcommon%2Fpdf%2Fsi-brochure%2FSI-Brochure-9.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACandela" class="Z3988"></span></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCIE2020" class="citation book cs1">CIE (2020). <a rel="nofollow" class="external text" href="https://cie.co.at/eilvterm/17-21-083"><i>CIE S 017:2020 ILV: International Lighting Vocabulary, 2nd edition</i></a> (2nd ed.). CIE.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=CIE+S+017%3A2020+ILV%3A+International+Lighting+Vocabulary%2C+2nd+edition.&rft.edition=2nd&rft.pub=CIE&rft.date=2020&rft.au=CIE&rft_id=https%3A%2F%2Fcie.co.at%2Feilvterm%2F17-21-083&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACandela" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1"><a rel="nofollow" class="external text" href="https://www.iso.org/standard/83178.html"><i>ISO/CIE 23539:2023 CIE TC 2-93 Photometry — The CIE system of physical photometry</i></a>. ISO/CIE. 2023. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.25039%2FIS0.CIE.23539.2023">10.25039/IS0.CIE.23539.2023</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=ISO%2FCIE+23539%3A2023+CIE+TC+2-93+Photometry+%E2%80%94+The+CIE+system+of+physical+photometry&rft.pub=ISO%2FCIE&rft.date=2023&rft_id=info%3Adoi%2F10.25039%2FIS0.CIE.23539.2023&rft_id=https%3A%2F%2Fwww.iso.org%2Fstandard%2F83178.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACandela" class="Z3988"></span></span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWyszeckiStiles1982" class="citation book cs1"><a href="/wiki/G%C3%BCnter_Wyszecki" title="Günter Wyszecki">Wyszecki, G.</a>; Stiles, W.S. (1982). <i>Color Science: Concepts and Methods, Quantitative Data and Formulae</i> (2nd ed.). Wiley-Interscience. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-471-02106-7" title="Special:BookSources/0-471-02106-7"><bdi>0-471-02106-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Color+Science%3A+Concepts+and+Methods%2C+Quantitative+Data+and+Formulae&rft.edition=2nd&rft.pub=Wiley-Interscience&rft.date=1982&rft.isbn=0-471-02106-7&rft.aulast=Wyszecki&rft.aufirst=G.&rft.au=Stiles%2C+W.S.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACandela" class="Z3988"></span></span> </li> <li id="cite_note-Webster-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-Webster_9-0">^</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="http://m-w.com/dictionary/candlepower">"Candlepower – Definition"</a>. <i>Merriam-Webster Dictionary</i><span class="reference-accessdate">. Retrieved <span class="nowrap">15 February</span> 2015</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Merriam-Webster+Dictionary&rft.atitle=Candlepower+%E2%80%93+Definition&rft_id=http%3A%2F%2Fm-w.com%2Fdictionary%2Fcandlepower&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACandela" class="Z3988"></span></span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20190919050548/https://www.bipm.org/utils/en/pdf/CGPM/Convocation-2018.pdf#page=25">"Convocation of the General Conference on Weights and Measures (26th meeting)"</a> <span class="cs1-format">(PDF)</span>. Versailles: Bureau International des Poids et Mesures. 13 November 2018. Archived from <a rel="nofollow" class="external text" href="https://www.bipm.org/utils/en/pdf/CGPM/Convocation-2018.pdf#page=25">the original</a> <span class="cs1-format">(PDF)</span> on 19 September 2019<span class="reference-accessdate">. Retrieved <span class="nowrap">10 February</span> 2019</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Convocation+of+the+General+Conference+on+Weights+and+Measures+%2826th+meeting%29&rft.place=Versailles&rft.pub=Bureau+International+des+Poids+et+Mesures&rft.date=2018-11-13&rft_id=https%3A%2F%2Fwww.bipm.org%2Futils%2Fen%2Fpdf%2FCGPM%2FConvocation-2018.pdf%23page%3D25&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACandela" class="Z3988"></span></span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBIPM2021" class="citation web cs1">BIPM (22 March 2021). <a rel="nofollow" class="external text" href="https://www.bipm.org/documents/20126/41489685/SI-App2-candela.pdf/1603b2e8-64a3-1fda-d9b4-7b748bad9c01?version=1.7&t=1637237944393&download=false">"Mise en pratique for the definition of the candela in the SI"</a>. <i>BIPM</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=BIPM&rft.atitle=Mise+en+pratique+for+the+definition+of+the+candela+in+the+SI&rft.date=2021-03-22&rft.au=BIPM&rft_id=https%3A%2F%2Fwww.bipm.org%2Fdocuments%2F20126%2F41489685%2FSI-App2-candela.pdf%2F1603b2e8-64a3-1fda-d9b4-7b748bad9c01%3Fversion%3D1.7%26t%3D1637237944393%26download%3Dfalse&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACandela" class="Z3988"></span></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation cs2"><a rel="nofollow" class="external text" href="https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf"><i>The International System of Units</i></a> <span class="cs1-format">(PDF)</span> (9th ed.), International Bureau of Weights and Measures, December 2022, p. 135, <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-92-822-2272-0" title="Special:BookSources/978-92-822-2272-0"><bdi>978-92-822-2272-0</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+International+System+of+Units&rft.pages=135&rft.edition=9th&rft.pub=International+Bureau+of+Weights+and+Measures&rft.date=2022-12&rft.isbn=978-92-822-2272-0&rft_id=https%3A%2F%2Fwww.bipm.org%2Fdocuments%2F20126%2F41483022%2FSI-Brochure-9-EN.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACandela" class="Z3988"></span></span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</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="http://www.sizes.com/units/hefner.htm">"Hefner unit, or Hefner candle"</a>. <i>Sizes.com</i>. 30 May 2007<span class="reference-accessdate">. Retrieved <span class="nowrap">25 February</span> 2009</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Sizes.com&rft.atitle=Hefner+unit%2C+or+Hefner+candle&rft.date=2007-05-30&rft_id=http%3A%2F%2Fwww.sizes.com%2Funits%2Fhefner.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACandela" class="Z3988"></span></span> </li> <li id="cite_note-Cottington-15"><span class="mw-cite-backlink">^ <a href="#cite_ref-Cottington_15-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Cottington_15-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCottington1986" class="citation journal cs1">Cottington, Ian E. (1986). <a rel="nofollow" class="external text" href="https://technology.matthey.com/article/30/2/84-95/">"Platinum and the Standard of Light: A Selective Review of Proposals Which Led to an International Unit of Luminous Intensity"</a>. <i>Platinum Metals Review</i>. <b>30</b> (2): 84.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Platinum+Metals+Review&rft.atitle=Platinum+and+the+Standard+of+Light%3A+A+Selective+Review+of+Proposals+Which+Led+to+an+International+Unit+of+Luminous+Intensity&rft.volume=30&rft.issue=2&rft.pages=84&rft.date=1986&rft.aulast=Cottington&rft.aufirst=Ian+E.&rft_id=https%3A%2F%2Ftechnology.matthey.com%2Farticle%2F30%2F2%2F84-95%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACandela" class="Z3988"></span></span> </li> <li id="cite_note-16"><span class="mw-cite-backlink"><b><a href="#cite_ref-16">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBarry_N._Taylor1992" class="citation book cs1">Barry N. Taylor (1992). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=y2-BDaoBVnwC&pg=PA18"><i>The Metric System: The International System of Units (SI)</i></a>. U. S. Department of Commerce. p. 18. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-941375-74-9" title="Special:BookSources/0-941375-74-9"><bdi>0-941375-74-9</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+Metric+System%3A+The+International+System+of+Units+%28SI%29&rft.pages=18&rft.pub=U.+S.+Department+of+Commerce&rft.date=1992&rft.isbn=0-941375-74-9&rft.au=Barry+N.+Taylor&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3Dy2-BDaoBVnwC%26pg%3DPA18&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACandela" class="Z3988"></span> (NIST Special Publication 330, 1991 ed.)</span> </li> <li id="cite_note-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-17">^</a></b></span> <span class="reference-text"> <a rel="nofollow" class="external text" href="http://www.bipm.org/utils/common/pdf/CGPM/CGPM9.pdf#page=54">Proceedings of the 9th CGPM</a>, 1948, page 54 (French)</span> </li> <li id="cite_note-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-18">^</a></b></span> <span class="reference-text">13th CGPM Resolution 5, CR, 104 (1967), and <i>Metrologia</i>, <b>4</b>, 43–44 (1968).</span> </li> <li id="cite_note-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-19">^</a></b></span> <span class="reference-text">16th CGPM Resolution 3, CR, 100 (1979), and <i>Metrologia</i>, <b>16</b>, 56 (1980).</span> </li> <li id="cite_note-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-20">^</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="http://physics.nist.gov/cuu/Units/candela.html">"Base unit definitions: Candela"</a>. <i>The <a href="/wiki/NIST" class="mw-redirect" title="NIST">NIST</a> Reference on Constants, Units, and Uncertainty</i><span class="reference-accessdate">. Retrieved <span class="nowrap">27 September</span> 2010</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=The+NIST+Reference+on+Constants%2C+Units%2C+and+Uncertainty&rft.atitle=Base+unit+definitions%3A+Candela&rft_id=http%3A%2F%2Fphysics.nist.gov%2Fcuu%2FUnits%2Fcandela.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACandela" class="Z3988"></span></span> </li> <li id="cite_note-21"><span class="mw-cite-backlink"><b><a href="#cite_ref-21">^</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="http://www.bipm.org/en/publications/mises-en-pratique">"<i>Mise en pratique</i> for the definition of the candela and associated derived units for photometric and radiometric quantities in the International System of Units (SI)"</a>. <i>SI Brochure Appendix 2</i>. Bureau International des Poids et Mesures. 22 March 2021<span class="reference-accessdate">. Retrieved <span class="nowrap">7 October</span> 2023</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=SI+Brochure+Appendix+2&rft.atitle=Mise+en+pratique+for+the+definition+of+the+candela+and+associated+derived+units+for+photometric+and+radiometric+quantities+in+the+International+System+of+Units+%28SI%29&rft.date=2021-03-22&rft_id=http%3A%2F%2Fwww.bipm.org%2Fen%2Fpublications%2Fmises-en-pratique&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACandela" class="Z3988"></span></span> </li> <li id="cite_note-22"><span class="mw-cite-backlink"><b><a href="#cite_ref-22">^</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.bipm.org/en/publications/si-brochure">"Units for photochemical and photobiological quantities"</a>. <i>SI Brochure Appendix 3</i>. Bureau International des Poids et Mesures. 22 March 2021<span class="reference-accessdate">. Retrieved <span class="nowrap">7 October</span> 2023</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=SI+Brochure+Appendix+3&rft.atitle=Units+for+photochemical+and+photobiological+quantities&rft.date=2021-03-22&rft_id=https%3A%2F%2Fwww.bipm.org%2Fen%2Fpublications%2Fsi-brochure&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACandela" class="Z3988"></span></span> </li> </ol></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1236075235">.mw-parser-output .navbox{box-sizing:border-box;border:1px solid #a2a9b1;width:100%;clear:both;font-size:88%;text-align:center;padding:1px;margin:1em auto 0}.mw-parser-output .navbox .navbox{margin-top:0}.mw-parser-output .navbox+.navbox,.mw-parser-output .navbox+.navbox-styles+.navbox{margin-top:-1px}.mw-parser-output .navbox-inner,.mw-parser-output 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colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:SI_units" title="Template:SI units"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:SI_units" title="Template talk:SI units"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:SI_units" title="Special:EditPage/Template:SI units"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="SI_units303" style="font-size:114%;margin:0 4em"><a href="/wiki/International_System_of_Units" title="International System of Units">SI units</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/SI_base_unit" title="SI base unit">Base units</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ampere" title="Ampere">ampere</a></li> <li><a class="mw-selflink selflink">candela</a></li> <li><a href="/wiki/Kelvin" title="Kelvin">kelvin</a></li> <li><a href="/wiki/Kilogram" title="Kilogram">kilogram</a></li> <li><a href="/wiki/Metre" title="Metre">metre</a></li> <li><a href="/wiki/Mole_(unit)" title="Mole (unit)">mole</a></li> <li><a href="/wiki/Second" title="Second">second</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/SI_derived_unit" title="SI derived unit">Derived units <br />with special names</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Becquerel" title="Becquerel">becquerel</a></li> <li><a href="/wiki/Coulomb" title="Coulomb">coulomb</a></li> <li><a href="/wiki/Celsius" title="Celsius">degree Celsius</a></li> <li><a href="/wiki/Farad" title="Farad">farad</a></li> <li><a href="/wiki/Gray_(unit)" title="Gray (unit)">gray</a></li> <li><a href="/wiki/Henry_(unit)" title="Henry (unit)">henry</a></li> <li><a href="/wiki/Hertz" title="Hertz">hertz</a></li> <li><a href="/wiki/Joule" title="Joule">joule</a></li> <li><a href="/wiki/Katal" title="Katal">katal</a></li> <li><a href="/wiki/Lumen_(unit)" title="Lumen (unit)">lumen</a></li> <li><a href="/wiki/Lux" title="Lux">lux</a></li> <li><a href="/wiki/Newton_(unit)" title="Newton (unit)">newton</a></li> <li><a href="/wiki/Ohm" title="Ohm">ohm</a></li> <li><a href="/wiki/Pascal_(unit)" title="Pascal (unit)">pascal</a></li> <li><a href="/wiki/Radian" title="Radian">radian</a></li> <li><a href="/wiki/Siemens_(unit)" title="Siemens (unit)">siemens</a></li> <li><a href="/wiki/Sievert" title="Sievert">sievert</a></li> <li><a href="/wiki/Steradian" title="Steradian">steradian</a></li> <li><a href="/wiki/Tesla_(unit)" title="Tesla (unit)">tesla</a></li> <li><a href="/wiki/Volt" title="Volt">volt</a></li> <li><a href="/wiki/Watt" title="Watt">watt</a></li> <li><a href="/wiki/Weber_(unit)" title="Weber (unit)">weber</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Non-SI_units_mentioned_in_the_SI" title="Non-SI units mentioned in the SI">Other accepted units</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Astronomical_unit" title="Astronomical unit">astronomical unit</a></li> <li><a href="/wiki/Dalton_(unit)" title="Dalton (unit)">dalton</a></li> <li><a href="/wiki/Day" title="Day">day</a></li> <li><a href="/wiki/Decibel" title="Decibel">decibel</a></li> <li><a href="/wiki/Degree_(angle)" title="Degree (angle)">degree of arc</a></li> <li><a href="/wiki/Electronvolt" title="Electronvolt">electronvolt</a></li> <li><a href="/wiki/Hectare" title="Hectare">hectare</a></li> <li><a href="/wiki/Hour" title="Hour">hour</a></li> <li><a href="/wiki/Litre" title="Litre">litre</a></li> <li><a href="/wiki/Minute" title="Minute">minute</a></li> <li><a href="/wiki/Minute_and_second_of_arc" title="Minute and second of arc">minute and second of arc</a></li> <li><a href="/wiki/Neper" title="Neper">neper</a></li> <li><a href="/wiki/Tonne" title="Tonne">tonne</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">See also</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Conversion_of_units" title="Conversion of units">Conversion of units</a></li> <li><a href="/wiki/Metric_prefix" title="Metric prefix">Metric prefixes</a></li> <li><a href="/wiki/Historical_definitions_of_the_SI_base_units" title="Historical definitions of the SI base units">Historical definitions of the SI base units</a></li> <li><a href="/wiki/2019_revision_of_the_SI" title="2019 revision of the SI">2019 revision of the SI</a></li> <li><a href="/wiki/System_of_units_of_measurement" title="System of units of measurement">System of units of measurement</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><span class="noviewer" typeof="mw:File"><span title="Category"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/31px-Symbol_category_class.svg.png 2x" data-file-width="180" data-file-height="185" /></span></span> <a href="/wiki/Category:SI_units" title="Category:SI units">Category</a></li></ul> </div></td></tr></tbody></table></div> <div 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