{"id":803,"date":"2017-12-04T09:01:04","date_gmt":"2017-12-04T14:01:04","guid":{"rendered":"https:\/\/designinglight.com\/?p=803"},"modified":"2017-12-03T16:49:26","modified_gmt":"2017-12-03T21:49:26","slug":"tm-30-rg-the-gamut-index","status":"publish","type":"post","link":"https:\/\/designinglight.com\/?p=803","title":{"rendered":"TM-30 Rg, The Gamut Index"},"content":{"rendered":"

In addition to an index that measures the fidelity of a light source to its reference source (R<\/em>f) IES TM-30 includes an index that indicates the change in saturation of colors called the Gamut Index and abbreviated R<\/em>g. \u00a0R<\/em>g is calculated using the same Color Evaluation Samples (CES) and underlying calculation engine as R<\/em>f, which makes TM-30 a cohesive system.<\/p>\n

Here’s how R<\/em>g works. \u00a0An R<\/em>g value of 100 indicates that, on average, the light source in question does not change the chroma, or saturation, of the 99 CES when compared to the reference light source. \u00a0An R<\/em>g value below 100 indicates that, on average, the light source renders colors as less saturated than the reference source, and an R<\/em>g value above 100 indicates that, on average, the light source renders colors as more saturated than the reference source.<\/p>\n

Since R<\/em>g is an average it says nothing about the possible change in chroma for any individual hue angle bin or for any individual color evaluation sample. \u00a0That’s ok, thought, because TM-30 also tells us the Rg values for each hue angle bin, and for each CES.<\/p>\n

Here’s an example of the graphic for the hue angle bins using the same light source as the previous post<\/a> on R<\/em>f.<\/p>\n

\"\"<\/a><\/p>\n

TM-30 doesn’t recommend any particular R<\/em>g or set of R<\/em>g values. \u00a0As with R<\/em>f, the interpretation of the information is left to the specifier. \u00a0Acceptable or desirable values will vary by application. \u00a0R<\/em>g doesn’t have a maximum or minimum value, but the possible range increases as R<\/em>f decreases, as shown below. The wedge to the left of the gray lines shows the range of possible R<\/em>g values, while the red dot represents the lamp we’ve been discussing.<\/p>\n

\"\"<\/a><\/p>\n

The R<\/em>g values are also presented in a Color Vector Graphic (CVG), as shown below. \u00a0The white circle is the normalized reference source. \u00a0The black circle is the lamp in question. \u00a0Where the black circle is inside the white, colors are desaturated. \u00a0Where the black circle is outside of the white, colors have increased saturation. \u00a0The colored arrows indicate the direction of saturation shift, and the direction of hue shift. \u00a0Arrows that point straight in or out show only saturation shift. \u00a0Arrows that show rotation left or right also indicate hue shift. \u00a0I know! \u00a0And, the next version of TM-30 will present a graph showing the hue shift!<\/p>\n

\"\"<\/a><\/p>\n

 <\/p>\n

Research is revealing that we shouldn’t treat all hue angle bins the same. \u00a0Bins 1 and 16, which include the most red, are indicative of preference and it seems likely that they will take on increasing importance in that role. \u00a0Some specifications are already acknowledging this. \u00a0For example, the Department of Defense recently re-issued the Unified Facilities Criteria for Military Medical Facilities <\/a>that\u00a0establishes the following requirements for light sources:<\/p>\n

\n

Fidelity Index: Rf \u2265 80,<\/p>\n

Relative Gamut Index: 97 to 110,<\/p>\n

Fidelity Index, Hue-Bin 1: \u00a0\u2265 78,<\/p>\n

Chroma Shift, Hue-Bin 1: -9% to +9%.<\/p>\n<\/blockquote>\n

Clearly, TM-30 permits us to be much more specific about the color rendering that is acceptable or desirable for a project. \u00a0Why bother with CRI anymore?<\/p>\n","protected":false},"excerpt":{"rendered":"

In addition to an index that measures the fidelity of a light source to its reference source (Rf) IES TM-30 includes an index that indicates the change in saturation of colors called the Gamut Index and abbreviated Rg. \u00a0Rg is calculated using the same Color Evaluation Samples (CES) and underlying calculation engine as Rf, which … Continue reading TM-30 Rg, The Gamut Index<\/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":[12,17,19],"tags":[27,68],"class_list":["post-803","post","type-post","status-publish","format-standard","hentry","category-color","category-light","category-lighting-profession","tag-color-rendering","tag-tm-30"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p4gZSw-cX","jetpack_sharing_enabled":true,"jetpack_likes_enabled":true,"jetpack-related-posts":[{"id":491,"url":"https:\/\/designinglight.com\/?p=491","url_meta":{"origin":803,"position":0},"title":"TM-30 and Color Gamut","author":"Jason Livingston","date":"August 26, 2015","format":false,"excerpt":"You may be familiar with the idea of a color gamut from displays or from RGB LED fixtures. In both cases the gamut describes the full range of colors that the device can create. In TM-30-15 IES Method for Evaluating Light Source Color Rendition gamut (Rg) has a somewhat different\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":567,"url":"https:\/\/designinglight.com\/?p=567","url_meta":{"origin":803,"position":1},"title":"NEMA Misrepresents IES TM-30","author":"Jason Livingston","date":"December 21, 2015","format":false,"excerpt":"On November 12 the National Electrical Manufacturers Association (NEMA) published a position paper on IES TM-30-15. The document is here. It seems to be a willful misunderstanding and misrepresentation of TM-30. Here\u2019s how\u2026 The paper opens with NEMA\u2019s support of an improved color metric but then goes on to say\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":803,"position":2},"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":[]},{"id":386,"url":"https:\/\/designinglight.com\/?p=386","url_meta":{"origin":803,"position":3},"title":"A New Color Rendering Metric","author":"Jason Livingston","date":"May 11, 2015","format":false,"excerpt":"At last week\u2019s Lightfair one of the presentations was Quantifying Color Rendition: A Path Forward. The presentation was the first public look at the (not yet approved) IES Method of quantifying color rendering. What is this new (not yet approved) IES Method? Let\u2019s start with a quick review of the\u2026","rel":"","context":"In "Color"","block_context":{"text":"Color","link":"https:\/\/designinglight.com\/?cat=12"},"img":{"alt_text":"CRI Test Color Sample SPDs","src":"https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2015\/05\/CIE_CRI_TCS_SPDs.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2015\/05\/CIE_CRI_TCS_SPDs.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2015\/05\/CIE_CRI_TCS_SPDs.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":787,"url":"https:\/\/designinglight.com\/?p=787","url_meta":{"origin":803,"position":4},"title":"TM-30 Rf: So Big, So Strong, So Smart!","author":"Jason Livingston","date":"November 6, 2017","format":false,"excerpt":"As we know, CRI Ra and TM-30 Rf are both measurements of color fidelity. \u00a0That is, they compare a test light source to a known reference light source and measure how well the test source matches the reference source. \u00a0One of the many shortcomings of CRI Ra is that it\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\/11\/CES-F32T8830.png?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2017\/11\/CES-F32T8830.png?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2017\/11\/CES-F32T8830.png?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2017\/11\/CES-F32T8830.png?resize=700%2C400&ssl=1 2x"},"classes":[]},{"id":796,"url":"https:\/\/designinglight.com\/?p=796","url_meta":{"origin":803,"position":5},"title":"Focal Point Introduces TM-30 Based “Preferred Light”","author":"Jason Livingston","date":"November 17, 2017","format":false,"excerpt":"Today Focal Point Lights of Chicago, IL introduced a series of fixtures that feature what they call Preferred Light. \u00a0Preferred Light is based on recent studies at PNNL and Penn State, plus their own study, and uses TM-30's Rf, Rg, and Hue Bin 16 values to establish a balance of\u2026","rel":"","context":"In "Color"","block_context":{"text":"Color","link":"https:\/\/designinglight.com\/?cat=12"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]}],"_links":{"self":[{"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/posts\/803","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=803"}],"version-history":[{"count":4,"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/posts\/803\/revisions"}],"predecessor-version":[{"id":811,"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/posts\/803\/revisions\/811"}],"wp:attachment":[{"href":"https:\/\/designinglight.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=803"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/designinglight.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=803"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/designinglight.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=803"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}