{"id":2618,"date":"2026-01-13T07:47:55","date_gmt":"2026-01-13T07:47:55","guid":{"rendered":"https:\/\/lightingrecipe.com\/?page_id=2618"},"modified":"2026-01-21T06:33:44","modified_gmt":"2026-01-21T06:33:44","slug":"m-edi-eml-caf-and-cs","status":"publish","type":"page","link":"https:\/\/lightingrecipe.com\/de\/m-edi-eml-caf-and-cs\/","title":{"rendered":"M-EDI, EML, CAF und CS"},"content":{"rendered":"<div class=\"wp-block-columns alignwide is-layout-flex wp-container-core-columns-is-layout-9d6595d7 wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\" style=\"flex-basis:100%\">\n<p class=\"has-black-color has-text-color has-link-color wp-elements-bee87a468518eeb5b7364738a07d08af\" style=\"font-size:15px\">Die Lichtindustrie erkennt inzwischen die nicht-visuellen Auswirkungen von Licht auf Gesundheit und zirkadiane Rhythmen an und treibt die Entwicklung standardisierter Kennzahlen f\u00fcr eine optimale melanopische Beleuchtung in unterschiedlichen Anwendungsbereichen voran. Die beiden am h\u00e4ufigsten verwendeten Metriken sind M-EDI und EML, die beide die biologische Wirkung von Licht messen \u2013 insbesondere im blau-lichtnahen Spektralbereich um 480 nm.<\/p>\n\n\n\n<p class=\"has-black-color has-text-color has-link-color has-medium-font-size wp-elements-a3b8ab23fe3d860bc36cdfb07ef99d9d\"><br><strong><br><em>Was ist M-EDI (Melanopische \u00e4quivalente Tageslichtbeleuchtungsst\u00e4rke)?<\/em><\/strong><\/p>\n\n\n\n<p class=\"has-black-color has-text-color has-link-color wp-elements-b4975066de0411eb8dabb46cf35dff36\" style=\"font-size:15px\"><br><br>Die Internationale Beleuchtungskommission (CIE) empfiehlt eine zirkadiane Metrik namens M-EDI. Sie quantifiziert die Lichtmenge einer Lichtquelle, die die melanopsinbasierte Photorezeption in der Netzhaut stimuliert, und basiert auf derselben grundlegenden Methodik wie EML.\nDiese Metrik bestimmt, wie viel Tageslicht erforderlich w\u00e4re, um die gleiche biologische Wirkung wie eine bestimmte Beleuchtungssituation zu erzielen. Der wesentliche Unterschied besteht darin, dass die Gr\u00f6\u00dfe von M-EDI als Beleuchtungsst\u00e4rke des CIE-Standardlichts D65 angegeben wird, die den gleichen Stimulus f\u00fcr intrinsisch photosensitive retinale Ganglienzellen (ipRGCs) liefert. Daher kann der M-EDI-Wert aus dem EML-Wert durch Multiplikation mit dem Koeffizienten 0,9063 umgerechnet werden.<br><br><em>Empfohlene Werte<\/em>Tags\u00fcber: &gt;250 M-EDI; nachts: &lt;50 M-EDI<\/p>\n\n\n\n<p class=\"has-black-color has-text-color has-link-color has-medium-font-size wp-elements-ab095862dc63cdcb73cfb99ef6a6a5ff\"><br><br><strong><em>Was ist \u00e4quivalente melanopische Beleuchtungsst\u00e4rke (EML)?<\/em><\/strong><\/p>\n\n\n\n<p class=\"has-black-color has-text-color has-link-color wp-elements-97daf462846fcdacfbf33cbc9ef4026f\" style=\"font-size:15px\"><br><br>Eine weitere zentrale Kennzahl ist EML, die im Rahmen des WELL Building Standards eingef\u00fchrt und verbreitet wurde. \u00c4hnlich wie M-EDI misst EML die zirkadiane Wirksamkeit von Licht, wird jedoch in Lux angegeben und so angepasst, dass die Empfindlichkeit melanopsinhaltiger intrinsisch photosensitiver retinaler Ganglienzellen (ipRGCs) ber\u00fccksichtigt wird, anstatt der klassischen photopischen Reaktion der Zapfen.<br><br>W\u00e4hrend die traditionelle Lux-Messung die vom menschlichen Auge wahrgenommene Helligkeit beschreibt, passt EML diese Bewertung an, um die biologische (nicht-visuelle) Wirkung von Licht auf das zirkadiane System widerzuspiegeln. EML erm\u00f6glicht es Lichtfachleuten zu beurteilen, wie effektiv eine Lichtquelle die Melanopsin-Rezeptoren stimuliert, die f\u00fcr die Regulation der biologischen Uhr essenziell sind.<br><br>Der WELL v2 Standard empfiehlt, morgens mindestens vier Stunden EML-Beleuchtung bereitzustellen, um den zirkadianen Rhythmus wirksam zu synchronisieren. Diese Lichtexposition unterst\u00fctzt gesunde Schlaf-Wach-Zyklen, verbessert die kognitive Leistungsf\u00e4higkeit und f\u00f6rdert die Emotionsregulation.<\/p>\n\n\n\n<p class=\"has-black-color has-text-color has-link-color wp-elements-e63f5f960a57d95789a187594cf12bdb\" style=\"font-size:15px\"><em>Empfohlene Bereiche<\/em>: Tags\u00fcber: &gt;150 EML; nachts: &lt;50 EML<br><br>Die Wahl zwischen M-EDI und EML h\u00e4ngt h\u00e4ufig vom Anwendungskontext ab. M-EDI ist in der wissenschaftlichen Standardisierung verankert und wird \u0448\u0438\u0440\u043e\u043a\u043e in Forschung und technischen Normen eingesetzt, w\u00e4hrend EML anwendungsorientiert ist und direkt mit praktischen Gesundheitsergebnissen sowie der WELL-Geb\u00e4udezertifizierung verkn\u00fcpft ist.<\/p>\n\n\n\n<p class=\"has-black-color has-text-color has-link-color wp-elements-61e86a58bf09354602fdf196d2d28532\" style=\"font-size:15px\"><\/p>\n\n\n\n<p class=\"has-black-color has-text-color has-link-color has-medium-font-size wp-elements-90fa9b807d32a1a4365aef956ae9a711\"><strong><em>Was ist der Circadian Action Factor (CAF)?<\/em><\/strong><\/p>\n\n\n\n<p class=\"has-black-color has-text-color has-link-color wp-elements-5904eb69bfe253a08d71368a12bdaaf4\" style=\"font-size:15px\">Das menschliche Auge enth\u00e4lt verschiedene Arten von Sehnervenzellen, von denen eine nicht der visuellen Informationsverarbeitung dient, sondern auf Lichtreize reagiert. Wenn Licht in das Auge eintritt, l\u00f6sen diese als intrinsisch photosensitive retinale Ganglienzellen (ipRGCs) bezeichneten Nervenzellen nicht-visuelle biologische Effekte aus. Diese Effekte beeinflussen ma\u00dfgeblich die Aussch\u00fcttung von Hormonen wie Melatonin und Cortisol.<br><br>Wenn ipRGCs hochfrequentem, energiereichem Licht ausgesetzt sind, hemmen sie die k\u00f6rpereigene Produktion von Melatonin, wodurch sich Menschen wach und energiegeladen f\u00fchlen. Bei der Exposition gegen\u00fcber energiearmem Licht steigt der Melatoninspiegel hingegen allm\u00e4hlich an, was Entspannung und M\u00fcdigkeit f\u00f6rdert. Daher ist Licht ein entscheidender externer Faktor, der den menschlichen zirkadianen Rhythmus beeinflusst.<br><br>Gall und Bieske entwickelten den Circadian Action Factor (CAF) als Indikator f\u00fcr die nicht-visuellen Auswirkungen von Licht auf die menschliche Gesundheit und das Wohlbefinden. Diese Kenngr\u00f6\u00dfe beschreibt, wie eine Lichtquelle das zirkadiane System beeinflusst, das wesentliche Prozesse wie Schlaf, Wachheit und kognitive Leistungsf\u00e4higkeit steuert. Die Metrik hilft Lichtplaner:innen zu verstehen, wie spezifische Lichtexpositionen auf das zirkadiane System wirken und zur Regulierung des zirkadianen Rhythmus beitragen.<br><br>CAF ist definiert als das Verh\u00e4ltnis der Lichtmenge, die das zirkadiane System beeinflusst, zur Lichtmenge, die f\u00fcr das Sehen nutzbar ist. Die Berechnung erfolgt auf Grundlage des vom Leuchtmittel emittierten Spektrums. Empfohlene CAF-Werte variieren je nach Tageszeit: Tags\u00fcber wird in der Regel ein h\u00f6herer CAF bevorzugt, um Wachheit und kognitive Leistungsf\u00e4higkeit zu f\u00f6rdern, w\u00e4hrend am Abend ein niedrigerer CAF besser geeignet ist, um Entspannung zu unterst\u00fctzen und den K\u00f6rper auf den Schlaf vorzubereiten. H\u00f6here CAF-Werte gehen mit einer st\u00e4rkeren Unterdr\u00fcckung der Melatoninproduktion einher.<br><br>Im Vergleich zur Farbtemperatur (CCT) ist CAF ein genauerer Indikator zur Vorhersage der melatoninunterdr\u00fcckenden Wirkung von Licht. Vorl\u00e4ufige Studien deuten darauf hin, dass CAF ein zuverl\u00e4ssigerer Index zur Untersuchung der physiologischen Auswirkungen von Licht auf den menschlichen K\u00f6rper sein k\u00f6nnte.<br><br>Gall schl\u00e4gt ideale Kombinationen aus einzelnen Aktivit\u00e4ten, dem Circadian Action Factor (CAF) und der Farbtemperatur von Lichtquellen vor, wie in der untenstehenden Abbildung dargestellt.<\/p>\n<\/div>\n<\/div>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full is-resized\"><img fetchpriority=\"high\" decoding=\"async\" width=\"1024\" height=\"585\" src=\"https:\/\/lightingrecipe.com\/wp-content\/uploads\/2025\/09\/unnamed-2-1.png\" alt=\"\" class=\"wp-image-1581\" style=\"width:535px;height:auto\" srcset=\"https:\/\/lightingrecipe.com\/wp-content\/uploads\/2025\/09\/unnamed-2-1.png 1024w, https:\/\/lightingrecipe.com\/wp-content\/uploads\/2025\/09\/unnamed-2-1-300x171.png 300w, https:\/\/lightingrecipe.com\/wp-content\/uploads\/2025\/09\/unnamed-2-1-768x439.png 768w\" sizes=\"(max-width: 1024px) 100vw, 1024px\" \/><\/figure>\n<\/div>\n\n\n<div class=\"wp-block-columns alignwide is-layout-flex wp-container-core-columns-is-layout-9d6595d7 wp-block-columns-is-layout-flex\">\n<div class=\"wp-block-column is-layout-flow wp-block-column-is-layout-flow\" style=\"flex-basis:100%\">\n<p class=\"has-black-color has-text-color has-link-color has-medium-font-size wp-elements-52c3b73d027103d5ecb66923b1df7262\"><strong><em>Was ist der Circadian Stimulus (CS)?<\/em><\/strong><br><\/p>\n\n\n\n<p class=\"has-black-color has-text-color has-link-color wp-elements-1a7f617dbacb792726d1424da1335ffc\" style=\"font-size:15px\">Die Circadian Stimulus (CS)-Metrik wurde von Forschenden des Lighting Research Center (LRC) entwickelt und dient zur Quantifizierung der Wirkung von Licht auf die akute Unterdr\u00fcckung der Melatoninproduktion, einem Marker f\u00fcr die Aktivierung des zirkadianen Systems. CS bewertet den Einfluss von Licht \u2013 basierend auf Spektrum, Intensit\u00e4t und Expositionsdauer \u2013 auf das menschliche zirkadiane System.<br><br>Im Gegensatz zu den von der CIE (M-EDI) und dem IWBI (EML) vorgeschlagenen Metriken ber\u00fccksichtigt die CS-Metrik nicht nur die Rolle der ipRGCs, sondern auch die Beitr\u00e4ge von St\u00e4bchen und Zapfen zu nicht-visuellen physiologischen Lichtreaktionen. Besonders hervorzuheben ist, dass CS das grundlegende Problem der Subadditivit\u00e4t im menschlichen zirkadianen System adressiert. Die Metrik gibt an, wie effektiv eine einst\u00fcndige Exposition gegen\u00fcber einer bestimmten Lichtst\u00e4rke und Wellenl\u00e4nge das zirkadiane System stimuliert \u2013 basierend auf ihrer F\u00e4higkeit, das Hormon Melatonin zu unterdr\u00fccken.<br><br>Der CS-Wert reicht von 0 (keine biologische Wirkung) bis 1 (maximale Aktivierung) und wird auf Grundlage der Reaktionscharakteristika melanopsinhaltiger Photorezeptorzellen in der Netzhaut berechnet. Diese Zellen regulieren die Melatoninsekretion und beeinflussen physiologische Funktionen wie den Schlaf-Wach-Rhythmus und die Wachsamkeit.<br><br>Durch die Echtzeitmessung von CS-Werten k\u00f6nnen Nutzer genau beurteilen, ob ihre Lichtumgebung den nat\u00fcrlichen zirkadianen Bed\u00fcrfnissen des K\u00f6rpers entspricht. So tr\u00e4gt ein hoher CS-Wert am Tag (empfohlener Bereich: 0,3\u20130,7) dazu bei, Wachheit und kognitive Leistungsf\u00e4higkeit zu steigern. Nachts sollte der CS-Wert unter 0,1 gehalten werden, um eine Unterdr\u00fcckung der Melatoninproduktion und Schlafst\u00f6rungen zu vermeiden. Dadurch ist die CS-Metrik besonders wertvoll f\u00fcr die Optimierung dynamischer Beleuchtungssysteme, etwa zirkadian-adaptiver Lichtl\u00f6sungen f\u00fcr Arbeitspl\u00e4tze, Gesundheitseinrichtungen und Wohnumgebungen.<\/p>\n<\/div>\n<\/div>\n\n\n\n<figure class=\"wp-block-video alignwide\"><video height=\"1080\" style=\"aspect-ratio: 1920 \/ 1080;\" width=\"1920\" controls src=\"https:\/\/lightingrecipe.com\/wp-content\/uploads\/2025\/08\/Lighting-Fundamentals-Part-6.mp4\"><\/video><\/figure>","protected":false},"excerpt":{"rendered":"<p>The lighting industry now recognizes the non-visual effects of light on health and circadian rhythms, driving the development of standardized metrics for optimal melanopic lighting across various settings. The two most widely used are M-EDI and EML, both of which measure light\u2019s biological impact\u2014especially around the blue-light spectrum (~480 nm). What is M-EDI (Melanopic Equivalent Daylight Illuminance)? The International Commission on Illumination (CIE) recommended a circadian metric called M-EDI. It quantifies the amount of light exposure from a source that stimulates melanopsin-based photoreception in the retina, and it shares the same fundamental methodology as EML. This metric determines how much daylight would be required to produce the same biological impact as a given lighting condition. The key difference is that the magnitude of M-EDI is expressed as the illuminance of the CIE standard illuminant D65 that delivers the same stimulus to ipRGCs. Thus, the M-EDI value can be converted from the EML value by multiplying it by a coefficient of 0.9063. Recommended levels: Daytime: &gt;250 M-EDI; Nighttime: &lt;50 M-EDI What is Equivalent Melanopic Lux (EML)? Another key metric is EML, introduced and popularized through the WELL Building Standard. Like M-EDI, EML measures the circadian effectiveness of light but is expressed in lux, modified to account for the sensitivity of melanopsin-containing ipRGCs, rather than the traditional photopic response of cones. While traditional lux measures brightness as perceived by the human eye, EML adjusts the measurement to reflect the biological (non-visual) impact of light on the circadian system. It allows lighting professionals to assess how effectively a light source stimulates melanopsin receptors, which are essential for regulating the biological clock. The WELL v2 Standard recommends at least four hours of EML lighting in the morning to effectively entrain the circadian rhythm. This exposure helps support healthy sleep-wake cycles, improve cognitive function, and enhance mood regulation. Suggested ranges: Daytime: &gt;150 EML; Nighttime: &lt;50 EML The choice between M-EDI and EML often depends on the context. M-EDI is rooted in scientific standardization and widely used in research and technical standards, while EML is application-focused and directly linked to practical health outcomes and WELL Building certification. What is Circadian Action Factor (CAF)? The human eye contains various types of optic nerve cells, one of which does not process visual information but instead responds to light stimuli. When light enters the eye, this type of optic nerve cell\u2014known as the intrinsically photosensitive retinal ganglion cell (ipRGC)\u2014triggers non-visual biological effects. These effects significantly influence the release of hormones such as melatonin and cortisol. When ipRGCs are exposed to high-frequency, high-energy light, they inhibit the body&#8217;s production of melatonin, making people feel alert and energized. Conversely, when exposed to low-energy light, melatonin levels gradually increase, making people feel relaxed and sleepy. Therefore, light serves as a crucial external factor affecting the human circadian rhythm. Gall and Bieske developed the Circadian Action Factor (CAF) as an indicator of the non-visual effects that light has on human health and well-being. It is a metric that describes how a light source influences the circadian system, which governs essential processes such as sleep, alertness, and cognitive performance. This metric helps lighting designers understand how specific light exposures impact the circadian system and contribute to circadian rhythm regulation. CAF is defined as the ratio of the amount of light affecting the circadian system to the amount of light useful for vision. It is calculated based on the light spectrum emitted by a device. Recommended CAF values vary depending on the time of day: a high CAF is typically preferred during the day to enhance alertness and cognitive function, while a lower CAF is more suitable in the evening to support relaxation and preparation for sleep. Higher CAF values correspond to greater melatonin suppression. Compared to color temperature, CAF is a more accurate indicator for predicting the melatonin-suppressing effects of light. Preliminary studies suggest that CAF may be a more reliable index for studying the physiological effects of light on the human body. Gall proposes ideal combinations of individual activities, the Circadian Action Factor (CAF), and the color temperature of light sources, as shown in the image below. What is Circadian Stimulus (CS)? Developed by researchers at the Lighting Research Center (LRC), the Circadian Stimulus (CS) metric is a method for quantifying light\u2019s impact on acute melatonin suppression, a marker of circadian system activation. It measures the effect of light\u2014based on spectrum, intensity, and duration\u2014on the human circadian system. In contrast to the metrics proposed by the CIE (M-EDI) and IWBI (EML), the CS metric considers not only the role of ipRGCs, but also the contributions of rods and cones in non-visual physiological responses to light. Notably, the CS metric addresses the fundamental problem of subadditivity in the human circadian system. It indicates how effectively a one-hour exposure to a specific light level and wavelength stimulates the circadian system, based on its ability to suppress the hormone melatonin. The CS value ranges from 0 (no biological effect) to 1 (maximum activation) and is calculated based on the response characteristics of melanopsin-containing photoreceptor cells in the retina. These cells regulate melatonin secretion and influence physiological functions such as the sleep-wake cycle and alertness. By measuring CS values in real time, users can accurately assess whether their light environment aligns with the body\u2019s natural circadian needs. For example, a high CS value during the day (recommended: 0.3\u20130.7) helps enhance alertness and cognitive performance. At night, the CS value should be kept below 0.1 to avoid melatonin suppression and sleep disturbances. This makes the CS metric particularly valuable for optimizing dynamic lighting systems, such as circadian-adaptive lighting solutions for workplaces, healthcare facilities, and residential environments.<\/p>","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_coblocks_attr":"","_coblocks_dimensions":"","_coblocks_responsive_height":"","_coblocks_accordion_ie_support":"","_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_glsr_average":0,"_glsr_ranking":0,"_glsr_reviews":0,"footnotes":""},"class_list":["post-2618","page","type-page","status-publish","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.6 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>M-EDI, EML, CAF, and CS -<\/title>\n<meta name=\"robots\" content=\"noindex, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<meta property=\"og:locale\" content=\"de_DE\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"M-EDI, EML, CAF, and CS -\" \/>\n<meta property=\"og:description\" content=\"The lighting industry now recognizes the non-visual effects of light on health and circadian rhythms, driving the development of standardized metrics for optimal melanopic lighting across various settings. The two most widely used are M-EDI and EML, both of which measure light\u2019s biological impact\u2014especially around the blue-light spectrum (~480 nm). What is M-EDI (Melanopic Equivalent Daylight Illuminance)? The International Commission on Illumination (CIE) recommended a circadian metric called M-EDI. It quantifies the amount of light exposure from a source that stimulates melanopsin-based photoreception in the retina, and it shares the same fundamental methodology as EML. This metric determines how much daylight would be required to produce the same biological impact as a given lighting condition. The key difference is that the magnitude of M-EDI is expressed as the illuminance of the CIE standard illuminant D65 that delivers the same stimulus to ipRGCs. Thus, the M-EDI value can be converted from the EML value by multiplying it by a coefficient of 0.9063. Recommended levels: Daytime: &gt;250 M-EDI; Nighttime: &lt;50 M-EDI What is Equivalent Melanopic Lux (EML)? Another key metric is EML, introduced and popularized through the WELL Building Standard. Like M-EDI, EML measures the circadian effectiveness of light but is expressed in lux, modified to account for the sensitivity of melanopsin-containing ipRGCs, rather than the traditional photopic response of cones. While traditional lux measures brightness as perceived by the human eye, EML adjusts the measurement to reflect the biological (non-visual) impact of light on the circadian system. It allows lighting professionals to assess how effectively a light source stimulates melanopsin receptors, which are essential for regulating the biological clock. The WELL v2 Standard recommends at least four hours of EML lighting in the morning to effectively entrain the circadian rhythm. This exposure helps support healthy sleep-wake cycles, improve cognitive function, and enhance mood regulation. Suggested ranges: Daytime: &gt;150 EML; Nighttime: &lt;50 EML The choice between M-EDI and EML often depends on the context. M-EDI is rooted in scientific standardization and widely used in research and technical standards, while EML is application-focused and directly linked to practical health outcomes and WELL Building certification. What is Circadian Action Factor (CAF)? The human eye contains various types of optic nerve cells, one of which does not process visual information but instead responds to light stimuli. When light enters the eye, this type of optic nerve cell\u2014known as the intrinsically photosensitive retinal ganglion cell (ipRGC)\u2014triggers non-visual biological effects. These effects significantly influence the release of hormones such as melatonin and cortisol. When ipRGCs are exposed to high-frequency, high-energy light, they inhibit the body&#8217;s production of melatonin, making people feel alert and energized. Conversely, when exposed to low-energy light, melatonin levels gradually increase, making people feel relaxed and sleepy. Therefore, light serves as a crucial external factor affecting the human circadian rhythm. Gall and Bieske developed the Circadian Action Factor (CAF) as an indicator of the non-visual effects that light has on human health and well-being. It is a metric that describes how a light source influences the circadian system, which governs essential processes such as sleep, alertness, and cognitive performance. This metric helps lighting designers understand how specific light exposures impact the circadian system and contribute to circadian rhythm regulation. CAF is defined as the ratio of the amount of light affecting the circadian system to the amount of light useful for vision. It is calculated based on the light spectrum emitted by a device. Recommended CAF values vary depending on the time of day: a high CAF is typically preferred during the day to enhance alertness and cognitive function, while a lower CAF is more suitable in the evening to support relaxation and preparation for sleep. Higher CAF values correspond to greater melatonin suppression. Compared to color temperature, CAF is a more accurate indicator for predicting the melatonin-suppressing effects of light. Preliminary studies suggest that CAF may be a more reliable index for studying the physiological effects of light on the human body. Gall proposes ideal combinations of individual activities, the Circadian Action Factor (CAF), and the color temperature of light sources, as shown in the image below. What is Circadian Stimulus (CS)? Developed by researchers at the Lighting Research Center (LRC), the Circadian Stimulus (CS) metric is a method for quantifying light\u2019s impact on acute melatonin suppression, a marker of circadian system activation. It measures the effect of light\u2014based on spectrum, intensity, and duration\u2014on the human circadian system. In contrast to the metrics proposed by the CIE (M-EDI) and IWBI (EML), the CS metric considers not only the role of ipRGCs, but also the contributions of rods and cones in non-visual physiological responses to light. Notably, the CS metric addresses the fundamental problem of subadditivity in the human circadian system. It indicates how effectively a one-hour exposure to a specific light level and wavelength stimulates the circadian system, based on its ability to suppress the hormone melatonin. The CS value ranges from 0 (no biological effect) to 1 (maximum activation) and is calculated based on the response characteristics of melanopsin-containing photoreceptor cells in the retina. These cells regulate melatonin secretion and influence physiological functions such as the sleep-wake cycle and alertness. By measuring CS values in real time, users can accurately assess whether their light environment aligns with the body\u2019s natural circadian needs. For example, a high CS value during the day (recommended: 0.3\u20130.7) helps enhance alertness and cognitive performance. At night, the CS value should be kept below 0.1 to avoid melatonin suppression and sleep disturbances. This makes the CS metric particularly valuable for optimizing dynamic lighting systems, such as circadian-adaptive lighting solutions for workplaces, healthcare facilities, and residential environments.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/lightingrecipe.com\/de\/m-edi-eml-caf-and-cs\/\" \/>\n<meta property=\"article:modified_time\" content=\"2026-01-21T06:33:44+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/lightingrecipe.com\/wp-content\/uploads\/2025\/09\/unnamed-2-1.png\" \/>\n\t<meta property=\"og:image:width\" content=\"1024\" \/>\n\t<meta property=\"og:image:height\" content=\"585\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Gesch\u00e4tzte Lesezeit\" \/>\n\t<meta name=\"twitter:data1\" content=\"5\u00a0Minuten\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/lightingrecipe.com\\\/m-edi-eml-caf-and-cs\\\/\",\"url\":\"https:\\\/\\\/lightingrecipe.com\\\/m-edi-eml-caf-and-cs\\\/\",\"name\":\"M-EDI, EML, CAF, and CS -\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/lightingrecipe.com\\\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\\\/\\\/lightingrecipe.com\\\/m-edi-eml-caf-and-cs\\\/#primaryimage\"},\"image\":{\"@id\":\"https:\\\/\\\/lightingrecipe.com\\\/m-edi-eml-caf-and-cs\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/lightingrecipe.com\\\/wp-content\\\/uploads\\\/2025\\\/09\\\/unnamed-2-1.png\",\"datePublished\":\"2026-01-13T07:47:55+00:00\",\"dateModified\":\"2026-01-21T06:33:44+00:00\",\"breadcrumb\":{\"@id\":\"https:\\\/\\\/lightingrecipe.com\\\/m-edi-eml-caf-and-cs\\\/#breadcrumb\"},\"inLanguage\":\"de\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\\\/\\\/lightingrecipe.com\\\/m-edi-eml-caf-and-cs\\\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"de\",\"@id\":\"https:\\\/\\\/lightingrecipe.com\\\/m-edi-eml-caf-and-cs\\\/#primaryimage\",\"url\":\"https:\\\/\\\/lightingrecipe.com\\\/wp-content\\\/uploads\\\/2025\\\/09\\\/unnamed-2-1.png\",\"contentUrl\":\"https:\\\/\\\/lightingrecipe.com\\\/wp-content\\\/uploads\\\/2025\\\/09\\\/unnamed-2-1.png\"},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\\\/\\\/lightingrecipe.com\\\/m-edi-eml-caf-and-cs\\\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\\\/\\\/lightingrecipe.com\\\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"M-EDI, EML, CAF, and CS\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\\\/\\\/lightingrecipe.com\\\/#website\",\"url\":\"https:\\\/\\\/lightingrecipe.com\\\/\",\"name\":\"\",\"description\":\"\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\\\/\\\/lightingrecipe.com\\\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"de\"}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"M-EDI, EML, CAF, and CS -","robots":{"index":"noindex","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"og_locale":"de_DE","og_type":"article","og_title":"M-EDI, EML, CAF, and CS -","og_description":"The lighting industry now recognizes the non-visual effects of light on health and circadian rhythms, driving the development of standardized metrics for optimal melanopic lighting across various settings. The two most widely used are M-EDI and EML, both of which measure light\u2019s biological impact\u2014especially around the blue-light spectrum (~480 nm). What is M-EDI (Melanopic Equivalent Daylight Illuminance)? The International Commission on Illumination (CIE) recommended a circadian metric called M-EDI. It quantifies the amount of light exposure from a source that stimulates melanopsin-based photoreception in the retina, and it shares the same fundamental methodology as EML. This metric determines how much daylight would be required to produce the same biological impact as a given lighting condition. The key difference is that the magnitude of M-EDI is expressed as the illuminance of the CIE standard illuminant D65 that delivers the same stimulus to ipRGCs. Thus, the M-EDI value can be converted from the EML value by multiplying it by a coefficient of 0.9063. Recommended levels: Daytime: &gt;250 M-EDI; Nighttime: &lt;50 M-EDI What is Equivalent Melanopic Lux (EML)? Another key metric is EML, introduced and popularized through the WELL Building Standard. Like M-EDI, EML measures the circadian effectiveness of light but is expressed in lux, modified to account for the sensitivity of melanopsin-containing ipRGCs, rather than the traditional photopic response of cones. While traditional lux measures brightness as perceived by the human eye, EML adjusts the measurement to reflect the biological (non-visual) impact of light on the circadian system. It allows lighting professionals to assess how effectively a light source stimulates melanopsin receptors, which are essential for regulating the biological clock. The WELL v2 Standard recommends at least four hours of EML lighting in the morning to effectively entrain the circadian rhythm. This exposure helps support healthy sleep-wake cycles, improve cognitive function, and enhance mood regulation. Suggested ranges: Daytime: &gt;150 EML; Nighttime: &lt;50 EML The choice between M-EDI and EML often depends on the context. M-EDI is rooted in scientific standardization and widely used in research and technical standards, while EML is application-focused and directly linked to practical health outcomes and WELL Building certification. What is Circadian Action Factor (CAF)? The human eye contains various types of optic nerve cells, one of which does not process visual information but instead responds to light stimuli. When light enters the eye, this type of optic nerve cell\u2014known as the intrinsically photosensitive retinal ganglion cell (ipRGC)\u2014triggers non-visual biological effects. These effects significantly influence the release of hormones such as melatonin and cortisol. When ipRGCs are exposed to high-frequency, high-energy light, they inhibit the body&#8217;s production of melatonin, making people feel alert and energized. Conversely, when exposed to low-energy light, melatonin levels gradually increase, making people feel relaxed and sleepy. Therefore, light serves as a crucial external factor affecting the human circadian rhythm. Gall and Bieske developed the Circadian Action Factor (CAF) as an indicator of the non-visual effects that light has on human health and well-being. It is a metric that describes how a light source influences the circadian system, which governs essential processes such as sleep, alertness, and cognitive performance. This metric helps lighting designers understand how specific light exposures impact the circadian system and contribute to circadian rhythm regulation. CAF is defined as the ratio of the amount of light affecting the circadian system to the amount of light useful for vision. It is calculated based on the light spectrum emitted by a device. Recommended CAF values vary depending on the time of day: a high CAF is typically preferred during the day to enhance alertness and cognitive function, while a lower CAF is more suitable in the evening to support relaxation and preparation for sleep. Higher CAF values correspond to greater melatonin suppression. Compared to color temperature, CAF is a more accurate indicator for predicting the melatonin-suppressing effects of light. Preliminary studies suggest that CAF may be a more reliable index for studying the physiological effects of light on the human body. Gall proposes ideal combinations of individual activities, the Circadian Action Factor (CAF), and the color temperature of light sources, as shown in the image below. What is Circadian Stimulus (CS)? Developed by researchers at the Lighting Research Center (LRC), the Circadian Stimulus (CS) metric is a method for quantifying light\u2019s impact on acute melatonin suppression, a marker of circadian system activation. It measures the effect of light\u2014based on spectrum, intensity, and duration\u2014on the human circadian system. In contrast to the metrics proposed by the CIE (M-EDI) and IWBI (EML), the CS metric considers not only the role of ipRGCs, but also the contributions of rods and cones in non-visual physiological responses to light. Notably, the CS metric addresses the fundamental problem of subadditivity in the human circadian system. It indicates how effectively a one-hour exposure to a specific light level and wavelength stimulates the circadian system, based on its ability to suppress the hormone melatonin. The CS value ranges from 0 (no biological effect) to 1 (maximum activation) and is calculated based on the response characteristics of melanopsin-containing photoreceptor cells in the retina. These cells regulate melatonin secretion and influence physiological functions such as the sleep-wake cycle and alertness. By measuring CS values in real time, users can accurately assess whether their light environment aligns with the body\u2019s natural circadian needs. For example, a high CS value during the day (recommended: 0.3\u20130.7) helps enhance alertness and cognitive performance. At night, the CS value should be kept below 0.1 to avoid melatonin suppression and sleep disturbances. This makes the CS metric particularly valuable for optimizing dynamic lighting systems, such as circadian-adaptive lighting solutions for workplaces, healthcare facilities, and residential environments.","og_url":"https:\/\/lightingrecipe.com\/de\/m-edi-eml-caf-and-cs\/","article_modified_time":"2026-01-21T06:33:44+00:00","og_image":[{"width":1024,"height":585,"url":"https:\/\/lightingrecipe.com\/wp-content\/uploads\/2025\/09\/unnamed-2-1.png","type":"image\/png"}],"twitter_card":"summary_large_image","twitter_misc":{"Gesch\u00e4tzte Lesezeit":"5\u00a0Minuten"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/lightingrecipe.com\/m-edi-eml-caf-and-cs\/","url":"https:\/\/lightingrecipe.com\/m-edi-eml-caf-and-cs\/","name":"M-EDI, EML, CAF, and CS -","isPartOf":{"@id":"https:\/\/lightingrecipe.com\/#website"},"primaryImageOfPage":{"@id":"https:\/\/lightingrecipe.com\/m-edi-eml-caf-and-cs\/#primaryimage"},"image":{"@id":"https:\/\/lightingrecipe.com\/m-edi-eml-caf-and-cs\/#primaryimage"},"thumbnailUrl":"https:\/\/lightingrecipe.com\/wp-content\/uploads\/2025\/09\/unnamed-2-1.png","datePublished":"2026-01-13T07:47:55+00:00","dateModified":"2026-01-21T06:33:44+00:00","breadcrumb":{"@id":"https:\/\/lightingrecipe.com\/m-edi-eml-caf-and-cs\/#breadcrumb"},"inLanguage":"de","potentialAction":[{"@type":"ReadAction","target":["https:\/\/lightingrecipe.com\/m-edi-eml-caf-and-cs\/"]}]},{"@type":"ImageObject","inLanguage":"de","@id":"https:\/\/lightingrecipe.com\/m-edi-eml-caf-and-cs\/#primaryimage","url":"https:\/\/lightingrecipe.com\/wp-content\/uploads\/2025\/09\/unnamed-2-1.png","contentUrl":"https:\/\/lightingrecipe.com\/wp-content\/uploads\/2025\/09\/unnamed-2-1.png"},{"@type":"BreadcrumbList","@id":"https:\/\/lightingrecipe.com\/m-edi-eml-caf-and-cs\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/lightingrecipe.com\/"},{"@type":"ListItem","position":2,"name":"M-EDI, EML, CAF, and CS"}]},{"@type":"WebSite","@id":"https:\/\/lightingrecipe.com\/#website","url":"https:\/\/lightingrecipe.com\/","name":"","description":"","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/lightingrecipe.com\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"de"}]}},"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/lightingrecipe.com\/de\/wp-json\/wp\/v2\/pages\/2618","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/lightingrecipe.com\/de\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/lightingrecipe.com\/de\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/lightingrecipe.com\/de\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/lightingrecipe.com\/de\/wp-json\/wp\/v2\/comments?post=2618"}],"version-history":[{"count":2,"href":"https:\/\/lightingrecipe.com\/de\/wp-json\/wp\/v2\/pages\/2618\/revisions"}],"predecessor-version":[{"id":2684,"href":"https:\/\/lightingrecipe.com\/de\/wp-json\/wp\/v2\/pages\/2618\/revisions\/2684"}],"wp:attachment":[{"href":"https:\/\/lightingrecipe.com\/de\/wp-json\/wp\/v2\/media?parent=2618"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}