{"id":5394,"date":"2026-04-09T13:16:19","date_gmt":"2026-04-09T17:16:19","guid":{"rendered":"https:\/\/designinglight.com\/?p=5394"},"modified":"2026-04-09T13:17:00","modified_gmt":"2026-04-09T17:17:00","slug":"a-brief-history-of-tm-30","status":"publish","type":"post","link":"https:\/\/designinglight.com\/?p=5394","title":{"rendered":"A Brief History of TM-30"},"content":{"rendered":"

Next Wednesday I\u2019ll be giving a presentation on LP-30<\/a> at LEDucation<\/a> (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.<\/p>\n

 <\/p>\n

The Color Rendering Index (CRI) was published by the International Commission on Illumination (Commission Internationale de l\u2019Eclairage or CIE) in 1965, primarily to deal with the problem of poor color rendering by early fluorescent lamps.\u00a0 It was a rather simple system that evaluated a light source by mathematically comparing the appearance of eight colors under the test light in question to their appearance under a standardized reference light source of the same correlated color temperature (CCT).\u00a0 It used the latest models of human vision, returned a single value that was easy to understand, and was quickly adopted by the industry.<\/p>\n

 <\/p>\n

CRI is a fidelity metric, meaning that the CRI value represents how closely the test light matches the reference light.\u00a0 Since this was the only system endorsed by a standards setting body, and became ubiquitous in our industry, many people came to believe that color rendering and fidelity were the same thing.<\/p>\n

 <\/p>\n

Perhaps unsurprisingly for a new system, errors were found and corrected in the 1974 update.\u00a0 The next update, in 1995, made only typographical corrections to the document. \u00a0Science has, of course, progressed since then with many components of the CRI calculation being withdrawn from use by the CIE as improved components were developed.\u00a0 The problems were well known and documented.\u00a0 For example, the IES Lighting Handbook 9th<\/sup> Edition<\/em>, published in 2000, included a brief discussion about this, and the 10th<\/sup> Edition<\/em>, published in 2011, included a table describing nine limitations of CRI. \u00a0Unfortunately, for what seem to be political, not scientific, reasons CRI hasn’t been updated since.\u00a0 In fact, as late as 2017 CIE 224:2017<\/a> continued to recommend CRI for general use.<\/p>\n

 <\/p>\n

The \u201climitations\u201d of CRI were exacerbated by LEDs, whose distinctive spectral shape frequently resulted in CRI values at odds with observed color rendering.\u00a0 By the mid-2010s the mismatch between CRI values and observations, combined with the clear trajectory LEDs were on to exceed the efficacy of other light sources and become the dominant source, meant something had to change.\u00a0 Since it was clear that CIE wasn\u2019t going to update CRI, members of the IES Color Committee formed a Task Group to evaluate the issue and develop a completely up to date, color rendering metric drawing on the best ideas other researchers had proposed over the years.\u00a0 The result, in 2015, was ANSI\/IES TM-30 Technical Memorandum: IES Method for Evaluating Light Source Color Rendition<\/em>, or TM-30.<\/p>\n

 <\/p>\n

Initially, we thought that TM-30\u2019s R<\/em>f<\/sub> (Fidelity Index) and R<\/em>g<\/sub> (Gamut Index) would be the key metrics, because they were similar to the CRI-GAI (Gamut Area Index<\/a>) system developed at Rensselear Polytechnic Institute as an improvement on CRI alone.\u00a0 Light sources that met certain values were described as Class A<\/a> under this system.\u00a0 TM-30 produces many more measurements, 149 in fact. We didn\u2019t know what they would mean or how they could be used, but thought the additional information would, at a minimum, be useful to researchers.<\/p>\n

 <\/p>\n

However, by 2018 several studies had been published with exciting results showing that by using four metrics instead of two (R<\/em>f<\/sub>, R<\/em>g<\/sub>, R<\/em>f,h1<\/sub> (fidelity of red), and R<\/em>cs,h1<\/sub> (chroma shift of red) TM-30 would allow users to evaluate a light source not only for fidelity, but for preference and vividness as well.\u00a0 The analysis of the studies became TM-30\u2019s Annex F, with the explanation of Preference (P), Vividness (V), and Fidelity (F) provided in Annex E, and the TM-30 reports were modified in 2020 to display the four key metrics and the PVF results.\u00a0 This was a huge improvement over CRI and gave designers the ability to tailor their color rendering goals to the needs of the project and the occupants.\u00a0 For example, projects such as hospitality benefit from a light source that renders colors in a way that is preferred vs high fidelity.<\/p>\n

 <\/p>\n

In the meantime, CIE did a more thorough evaluation of R<\/em>f<\/sub> (specifically their version of R<\/em>f<\/sub> as defined in CIE 224:2017) and in January of 2025 CIE PS 002:2025<\/a> recommended the industry transition away from CRI to R<\/em>f<\/sub>.\u00a0 The IES, on the other hand, takes the position that it doesn\u2019t make sense to simply replace one fidelity metric with another.\u00a0 Instead, they recommend the industry adopt the entire suite of TM-30 metrics, including the evaluation of PVF.<\/p>\n

 <\/p>\n

The problem for specifiers, at that point, was how to use this information.\u00a0 What are preference, vividness and fidelity?\u00a0 How do I find a preferred source, and how do I specify it?\u00a0 What TM-30 information do I collect\/need at each phase of the design?\u00a0 What language can I put in my specification?\u00a0 While many of us on the Color Committee (and others) gave seminars and webinars over the years, there are still many who aren\u2019t certain how to use TM-30.<\/p>\n

 <\/p>\n

To provide a clear answer to those questions the Color Committee formed a Task Group to write a user\u2019s guide to TM-30.\u00a0 For more than three years a half dozen people wrote, illustrated, re-wrote and re-illustrated ANSI\/IES LP-30<\/em>\u00a0Lighting Practice: A Comprehensive Guide to Specifying Color Rendition \u2014 Concepts, Criteria, and Implementation<\/em>.\u00a0 LP-30 provides the industry with a guide to specifying color rendition with TM-30 by expanding on the framework of TM-30 Annex E. The goal of this document is to help lighting specifiers understand color rendition considerations for a project and appropriately gather, interpret, and apply TM-30 metrics. It provides a thorough description of how color rendition may be considered in each phase of design, explains color rendition goals and color rendition related steps in the design process, related activities that occur during those steps, and examples of the deliverables in each design phase.<\/p>\n

 <\/p>\n

LP-30 is available in the IES Online Lighting Library and the IES Store<\/a>.<\/p>\n

 <\/p>\n

For those of you not able to make it to LEDucation, I will also be giving a presentation on LP-30 at ArchLIGHT Summit<\/a> in September. \u00a0There, we hope to have a color rendering demonstration to illustrate the ideas discussed during the presentation.<\/p>\n","protected":false},"excerpt":{"rendered":"

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.   The Color Rendering Index (CRI) was published by the International Commission on Illumination (Commission Internationale de l\u2019Eclairage … Continue reading A Brief History of TM-30<\/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_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":[12,21,19],"tags":[27,68],"class_list":["post-5394","post","type-post","status-publish","format-standard","hentry","category-color","category-education","category-lighting-profession","tag-color-rendering","tag-tm-30"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p4gZSw-1p0","jetpack_sharing_enabled":true,"jetpack_likes_enabled":true,"jetpack-related-posts":[{"id":1977,"url":"https:\/\/designinglight.com\/?p=1977","url_meta":{"origin":5394,"position":0},"title":"The Strength of TM-30","author":"Jason Livingston","date":"September 28, 2021","format":false,"excerpt":"The strength of using TM-30 to evaluate light source color rendering.","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\/2021\/09\/Screen-Shot-2021-09-28-at-7.51.45-AM.png?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2021\/09\/Screen-Shot-2021-09-28-at-7.51.45-AM.png?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2021\/09\/Screen-Shot-2021-09-28-at-7.51.45-AM.png?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2021\/09\/Screen-Shot-2021-09-28-at-7.51.45-AM.png?resize=700%2C400&ssl=1 2x, https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2021\/09\/Screen-Shot-2021-09-28-at-7.51.45-AM.png?resize=1050%2C600&ssl=1 3x, https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2021\/09\/Screen-Shot-2021-09-28-at-7.51.45-AM.png?resize=1400%2C800&ssl=1 4x"},"classes":[]},{"id":954,"url":"https:\/\/designinglight.com\/?p=954","url_meta":{"origin":5394,"position":1},"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":1815,"url":"https:\/\/designinglight.com\/?p=1815","url_meta":{"origin":5394,"position":2},"title":"New TM-30 Tutorial Available","author":"Jason Livingston","date":"July 7, 2021","format":false,"excerpt":"Many of us on the IES Color Committee, myself included, have written and spoken about TM-30 and how to use it. I've written posts on this blog (click on the color rendering tag to see them all), authored articles, spoken at IES Annual Conferences, given webinars to architects and lighting\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":506,"url":"https:\/\/designinglight.com\/?p=506","url_meta":{"origin":5394,"position":3},"title":"Xicato Publishes IES TM-30-15 Results for its LED Modules","author":"Jason Livingston","date":"September 24, 2015","format":false,"excerpt":"In a first (as far as I know) LED manufacturer Xicato has published TM-30 results for some of its modules alongside the CRI results for Ra and R9. \u00a0Menko de Roos, CEO of Xicato, says \"At Xicato we are very supportive of TM-30-15 overall and recognize the need for an\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":2447,"url":"https:\/\/designinglight.com\/?p=2447","url_meta":{"origin":5394,"position":4},"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":780,"url":"https:\/\/designinglight.com\/?p=780","url_meta":{"origin":5394,"position":5},"title":"The Advantages of TM-30","author":"Jason Livingston","date":"October 30, 2017","format":false,"excerpt":"In this series of posts about IES TM-30-15 I've discussed the problems with CRI and the resistance to adopting TM-30. \u00a0In this post I'll discuss the advantages of TM-30 over CRI, and what TM-30 is and isn't. Color Samples Like CRI, TM-30 compares color samples rendered by a given test\u2026","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\/2017\/10\/TM-30-Bins.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2017\/10\/TM-30-Bins.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2017\/10\/TM-30-Bins.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]}],"_links":{"self":[{"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/posts\/5394","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=5394"}],"version-history":[{"count":6,"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/posts\/5394\/revisions"}],"predecessor-version":[{"id":5401,"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/posts\/5394\/revisions\/5401"}],"wp:attachment":[{"href":"https:\/\/designinglight.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=5394"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/designinglight.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=5394"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/designinglight.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=5394"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}