{"id":2910,"date":"2023-01-02T13:59:29","date_gmt":"2023-01-02T18:59:29","guid":{"rendered":"https:\/\/designinglight.com\/?p=2910"},"modified":"2023-01-02T13:59:29","modified_gmt":"2023-01-02T18:59:29","slug":"cct-doesnt-predict-circadian-impact","status":"publish","type":"post","link":"https:\/\/designinglight.com\/?p=2910","title":{"rendered":"CCT Doesn’t Predict Circadian Impact"},"content":{"rendered":"

Two of my IES Color Committee friends and colleagues, Tony Esposito and Kevin Houser, have just published a paper in Scientific Reports<\/a> that looks at the common assumption that CCT can be used to assess circadian entrainment and other biological impacts of light. The assumption by many is that high CCT light contains the blue wavelengths necessary for circadian entrainment, and that assumption is emphasized in the marketing a wide range of tunable white fixtures.<\/p>\n

Their study used a five-channel LED system in a full scale model of a room. The LEDs were used to create over 200,000 SPDs across a range of color temperatures and illuminance levels. They found that CCT alone is not an accurate predictor of the spectral content of the light. Since the three major systems used to predict \u201cbiological potency\u201d of light – CIE melanopic Equivalent Daylight Illuminance (mel-EDI), Equivalent Melanopic Lux (EML), and Circadian Stimulus (CS) – all use spectral analysis to understand biological impact, using CCT alone is simply inadequate. High CCT may correspond to circadian response, or it may not. They conclude their paper by saying<\/p>\n

\n

The lighting industry is experiencing rapid transformation as we expand our awareness of the non-visual impacts of light on humans. It is pertinent that we develop measures, methods, and strategies for implementing architectural lighting solutions that support these non-visual impacts. To do so, we need accurate and predictive measures of the biological potency of light that are based on sound science. In this study, we have argued that CCT is conceptually inappropriate for this purpose and performed a numerical analysis demonstrating that significant variation in circadian stimulus and melanopic equivalent daylight illuminance exists at any fixed CCT and photopic illuminance, making CCT an inappropriate proxy of those measures. Using CCT as a proxy for the biological potency of light cannot be justified.<\/p>\n<\/blockquote>\n

Understanding that CCT doesn\u2019t correspond with biological impact, it becomes important that designers understand the three systems and push manufacturers to begin providing the relevant information.<\/p>\n","protected":false},"excerpt":{"rendered":"

Two of my IES Color Committee friends and colleagues, Tony Esposito and Kevin Houser, have just published a paper in Scientific Reports that looks at the common assumption that CCT can be used to assess circadian entrainment and other biological impacts of light. The assumption by many is that high CCT light contains the blue … Continue reading CCT Doesn’t Predict Circadian Impact<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[6,12,3,19,10],"tags":[],"class_list":["post-2910","post","type-post","status-publish","format-standard","hentry","category-calculations","category-color","category-health","category-lighting-profession","category-luminaires"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p4gZSw-KW","jetpack_sharing_enabled":true,"jetpack_likes_enabled":true,"jetpack-related-posts":[{"id":738,"url":"https:\/\/designinglight.com\/?p=738","url_meta":{"origin":2910,"position":0},"title":"IES Disagrees With AMA on Night Time Outdoor Lighting","author":"Jason Livingston","date":"June 28, 2017","format":false,"excerpt":"Last year the AMA issued Policy H-135.927\u00a0Human and Environmental Effects of Light Emitting Diode (LED) Community Lighting, which recommended, among other things, that LED outdoor lighting should have a CCT of 3000 K or below. \u00a0The AMA made this recommendation thinking that lower correlated color temperatures contain less blue light,\u2026","rel":"","context":"In "Color"","block_context":{"text":"Color","link":"https:\/\/designinglight.com\/?cat=12"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":838,"url":"https:\/\/designinglight.com\/?p=838","url_meta":{"origin":2910,"position":1},"title":"Night Shift? Not Quite.","author":"Jason Livingston","date":"May 14, 2018","format":false,"excerpt":"We've all heard about the effect blue light can have on our circadian rhythms. \u00a0It can suppress the release of melatonin, which can delay sleep and reduce sleep quality with possible long-term health consequences. \u00a0Circadian disruption has been associated with depression and increased risk of diseases such as diabetes, obesity\u2026","rel":"","context":"In "Health"","block_context":{"text":"Health","link":"https:\/\/designinglight.com\/?cat=3"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":1650,"url":"https:\/\/designinglight.com\/?p=1650","url_meta":{"origin":2910,"position":2},"title":"What is the Reference Illuminant?","author":"Jason Livingston","date":"May 11, 2021","format":false,"excerpt":"Over the past few months I\u2019ve had a manufacturer, a sales rep, and a lighting designer all tell me they think CRI compares a light source to daylight.\u00a0\u00a0When I tried to correct one of them the reply was an acknowledgment that an incandescent source is normally used, but daylight can\u2026","rel":"","context":"In \"color rendering\"","block_context":{"text":"color rendering","link":"https:\/\/designinglight.com\/?tag=color-rendering"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":4039,"url":"https:\/\/designinglight.com\/?p=4039","url_meta":{"origin":2910,"position":3},"title":"How are CCT and Duv Calculated? IES TM-40","author":"Jason Livingston","date":"September 30, 2024","format":false,"excerpt":"If you look up the definition of Correlated Color Temperature (CCT) in IES LS-1 you'll find, \"The absolute temperature of a blackbody whose chromaticity most nearly resembles that of the light source.\" \u00a0It seems straightforward. \u00a0The spectra of non-incandescent light sources don't exactly match a blackbody radiator. \u00a0They'll plot off\u2026","rel":"","context":"In "Color"","block_context":{"text":"Color","link":"https:\/\/designinglight.com\/?cat=12"},"img":{"alt_text":"C78.377 chromaticity quadrangles","src":"https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2024\/09\/3.8-C78.377-300x300.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":954,"url":"https:\/\/designinglight.com\/?p=954","url_meta":{"origin":2910,"position":4},"title":"Misunderstanding CRI","author":"Jason Livingston","date":"April 8, 2019","format":false,"excerpt":"Discusses a common misuse of CRI and how it is corrected with TM-30.","rel":"","context":"In "Color"","block_context":{"text":"Color","link":"https:\/\/designinglight.com\/?cat=12"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2019\/04\/LED90.png?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2019\/04\/LED90.png?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2019\/04\/LED90.png?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":1264,"url":"https:\/\/designinglight.com\/?p=1264","url_meta":{"origin":2910,"position":5},"title":"Standard 189.1 Now Includes TM-30 Requirements","author":"Jason Livingston","date":"August 19, 2020","format":false,"excerpt":"Yesterday an addendum to ANSI\/ASHRAE\/ICC\/USGBC\/IES Standard 189.1-2017 Standard for the Design of High-Performance Green Buildings was published. The addendum makes changes to Section 8.3.5, which covers lighting. One of the biggest changes is to add TM-30 color rendition criteria to the section on Indoor Lighting Quality. Here's the relevant text:\u2026","rel":"","context":"In "Codes"","block_context":{"text":"Codes","link":"https:\/\/designinglight.com\/?cat=5"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]}],"_links":{"self":[{"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/posts\/2910","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/designinglight.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2910"}],"version-history":[{"count":1,"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/posts\/2910\/revisions"}],"predecessor-version":[{"id":2911,"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/posts\/2910\/revisions\/2911"}],"wp:attachment":[{"href":"https:\/\/designinglight.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2910"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/designinglight.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2910"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/designinglight.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2910"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}