{"id":930,"date":"2019-02-05T09:00:39","date_gmt":"2019-02-05T14:00:39","guid":{"rendered":"https:\/\/designinglight.com\/?p=930"},"modified":"2019-02-04T16:29:25","modified_gmt":"2019-02-04T21:29:25","slug":"fixing-cri-but-not-really","status":"publish","type":"post","link":"https:\/\/designinglight.com\/?p=930","title":{"rendered":"Fixing CRI, But Not Really"},"content":{"rendered":"\n

A couple of weeks ago the\u00a0Global Lighting Association\u00a0<\/a>(GLA) published\u00a0Application of CIE 13.3-1995 with Associated CRI-based Color Rendition Properties<\/em>.\u00a0\u00a0It proposes TM-30 like metrics to supplement CRI\u00a0R<\/em>a<\/sub>.\u00a0\u00a0Specifically, it proposes a color gamut index, G<\/em>a<\/sub>, that is similar to TM-30\u2019s R<\/em>g <\/sub>and a set of chroma indices, C<\/em>i<\/sub>, similar to TM-30\u2019s\u00a0R<\/em>ch,hj<\/sub>.\u00a0\u00a0At first glance I can see some specifiers getting excited about this.\u00a0\u00a0Since it\u2019s based on CRI it\u2019s already somewhat familiar so it should be easier to learn.\u00a0\u00a0But\u2026<\/p>\n\n\n\n

The first part is the problem \u2013 it\u2019s based on CRI, which has well known and well documented problems and shortcomings.  As described in The Lighting Handbook, 10th<\/sup>Ed.<\/em>and IES DG-1 Color and Illumination<\/em>, they include:<\/p>\n\n\n\n

Averaging the Color Shifts<\/strong>.\u00a0CRI is computed by averaging the color shifts of the eight color samples.\u00a0\u00a0A light source can render one sample very poorly and still achieve an acceptable score.\u00a0\u00a0The Chroma Indices attempt to resolve this, but there\u2019s a problem with the eight color samples, which is next on our list.<\/p>\n\n\n\n

Test Color Samples.<\/strong>\u00a0The eight color samples are all of moderate saturation, so saturated colors can be rendered poorly even when CRI is high.\u00a0\u00a0More importantly, the eight color samples are A) not based on any real-world objects B) don\u2019t adequately cover the visible spectrum.\u00a0\u00a0The latter is significant because it means that some wavelengths play an outsized role in determining CRI.\u00a0\u00a0Manufacturers can use this to optimize (or cheat) their spectrum to achieve a higher CRI than visual inspection would warrant.\u00a0\u00a0This is why TM-30 uses 99 color samples drawn from real world objects.<\/p>\n\n\n\n

Color Space<\/strong>.\u00a0\u00a0CRI is calculated in the CIE 1964 color space, which is no longer recommended for any other use because it is outdated.<\/p>\n\n\n\n

Penalties for all Chromaticity Shifts<\/strong>.\u00a0\u00a0As a fidelity metric, CRI penalizes all chromaticity shifts even though research has shown that certain increases in chroma are preferred.\u00a0\u00a0Again, it seems that\u00a0C<\/em>i\u00a0<\/sub>is intended to address this, but it doesn\u2019t resolve the other problems with CRI.\u00a0<\/p>\n\n\n\n

Chromatic Adaptation<\/strong>.\u00a0The chromatic adaptation transform used in CRI has been shown to perform poorly and is no longer recommended for any application.<\/p>\n\n\n\n

CRI served the industry (relatively) well, but its time is over.  Layering new calculations on top of CRI\u2019s flawed foundation doesn\u2019t make it better. I know TM-30 can be tough.  But it works.  It tells us what we want to know at the level of detail we need for a given project, and it\u2019s accurate.  The IES has moved on and the CIE seems to be leaning in that direction as well.  So should you!<\/p>\n","protected":false},"excerpt":{"rendered":"

A couple of weeks ago the\u00a0Global Lighting Association\u00a0(GLA) published\u00a0Application of CIE 13.3-1995 with Associated CRI-based Color Rendition Properties.\u00a0\u00a0It proposes TM-30 like metrics to supplement CRI\u00a0Ra.\u00a0\u00a0Specifically, it proposes a color gamut index, Ga, that is similar to TM-30\u2019s Rg and a set of chroma indices, Ci, similar to TM-30\u2019s\u00a0Rch,hj.\u00a0\u00a0At first glance I can see some specifiers … Continue reading Fixing CRI, But Not Really<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_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}},"categories":[12],"tags":[26,68],"class_list":["post-930","post","type-post","status-publish","format-standard","hentry","category-color","tag-cri","tag-tm-30"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p4gZSw-f0","jetpack_sharing_enabled":true,"jetpack_likes_enabled":true,"jetpack-related-posts":[{"id":2447,"url":"https:\/\/designinglight.com\/?p=2447","url_meta":{"origin":930,"position":0},"title":"Manufacturers Don’t Understand Color Rendering","author":"Jason Livingston","date":"March 17, 2022","format":false,"excerpt":"I attended LEDucation in New York City this week. \u00a0While there I spoke to over two dozen manufacturers, none of whom understood color rendering beyond the (partially accurate) belief that higher CRI is better. \u00a0My conversations when like this. Lighting Salesperson: \"Our color rendering is great. \u00a0Our CRI is over\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":4324,"url":"https:\/\/designinglight.com\/?p=4324","url_meta":{"origin":930,"position":1},"title":"CIE Recommends Transition from CRI to Rf","author":"Jason Livingston","date":"January 21, 2025","format":false,"excerpt":"Earlier this month, CIE published CIE Position Statement on Color Quality Metrics, in which it recommends the lighting industry transition from the outdated and sometimes inaccurate General Color Rendering Index (CRI) to the General Color Fidelity Index (Rf ) defined in CIE 224:2017. \u00a0The position statement notes that problems with\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":954,"url":"https:\/\/designinglight.com\/?p=954","url_meta":{"origin":930,"position":2},"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":5394,"url":"https:\/\/designinglight.com\/?p=5394","url_meta":{"origin":930,"position":3},"title":"A Brief History of TM-30","author":"Jason Livingston","date":"April 9, 2026","format":false,"excerpt":"Next Wednesday I\u2019ll be giving a presentation on LP-30 at LEDucation (hope to see you there!), and in preparing for it I\u2019ve been reflecting on how far we\u2019ve come in our understanding and evaluation of color rendering. \u00a0 The Color Rendering Index (CRI) was published by the International Commission on\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":3148,"url":"https:\/\/designinglight.com\/?p=3148","url_meta":{"origin":930,"position":4},"title":"AI and the Internet Need to Learn Color Rendering","author":"Jason Livingston","date":"March 28, 2023","format":false,"excerpt":"Recently a colleague of mine from the IES Color Committee asked of one of the new AIs \"Tell me about color rendering.\" \u00a0If we assume that the answer was formulated based on information about color rendering that is available on the internet we have a problem because the answer the\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":526,"url":"https:\/\/designinglight.com\/?p=526","url_meta":{"origin":930,"position":5},"title":"CRI Inches Forward","author":"Jason Livingston","date":"November 1, 2015","format":false,"excerpt":"The CIE\u2019s Color Rendition Index (CRI) has long had several known weaknesses including outdated components of the calculations, a limited set of color samples, and standard reporting of only one piece of data (the average color distortion of the first eight colors, known as the General Color Rendering Index or\u2026","rel":"","context":"In 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