{"id":787,"date":"2017-11-06T10:15:07","date_gmt":"2017-11-06T15:15:07","guid":{"rendered":"https:\/\/designinglight.com\/?p=787"},"modified":"2017-11-05T12:08:58","modified_gmt":"2017-11-05T17:08:58","slug":"tm-30-rf-so-big-so-strong-so-smart","status":"publish","type":"post","link":"https:\/\/designinglight.com\/?p=787","title":{"rendered":"TM-30 Rf: So Big, So Strong, So Smart!"},"content":{"rendered":"

As we know, CRI R<\/em>a and TM-30 R<\/em>f 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 R<\/em>a is that it provides us with a single value. \u00a0That single value is easy to use, but doesn’t tell us anything about what colors will have increased saturation, decreased saturation, hue change, or will be unaffected.<\/p>\n

TM-30 is a tougher test than CRI, so how do R<\/em>f and R<\/em>a values relate? \u00a0Lamps with R<\/em>a values below about 70 tend to have higher R<\/em>f values, while lamps with higher R<\/em>a values tend to have reduced R<\/em>f values. \u00a0Of course, this doesn’t mean that the lamps we think of as better have suddenly become worse, it’s just that we’re scoring on a different scale. \u00a0This means that we can’t draw direct comparisons. \u00a0For example, Energy Star requires that lamps have a minimum CRI R<\/em>a of 80, but that doesn’t mean that they should also have a minimum R<\/em>f of 80. \u00a0Different tests give different results and we have to be careful not to apply the meaning of one to the scores of the other.<\/p>\n

IES TM-30’s R<\/em>f mathematically compares the appearance, under a test light source, of 99 color evaluation samples (CES) that are derived from real world objects, to the CES appearance under a reference light source of the same CCT. \u00a0The distance of the color shift for each CES is measured in the CAM02-UCS color space and averaged. \u00a0Throw in a lot of calculus (which we don’t need to get into) and voila, the R<\/em>f value. \u00a0It’s important to remember that what we get is just a number. \u00a0TM-30 doesn’t qualify any of the results as good or bad, desirable or undesirable. \u00a0It presents information to the lighting specifier and allows the specifier to apply education, professional experience, and knowledge about the project to determine whether or not a given light source is appropriate.<\/p>\n

As with R<\/em>a, the single value of R<\/em>f conveys limited information. \u00a0It is more<\/strong> accurate<\/strong>, but still only tells us the average match or mismatch between the two light sources. \u00a0What makes TM-30 so powerful and useful is that it tells us much more if we want to know. \u00a0For example, using the Calculation Tool that can be downloaded with the purchase of TM-30 (which I wish the IES would make freely available), we can see that one common F32T8\/830 has the following characteristics:<\/p>\n

R<\/em>f \u00a0 78
\nR<\/em>g \u00a0 102
\nCCT \u00a0 2943
\nDuv \u00a0 0.0014
\nR<\/em>a \u00a0 85<\/p>\n

This lamp has moderately good fidelity (R<\/em>f), a slight increase in saturation (R<\/em>g), has a CCT of just under 3000K, and is slightly above the black body locus and therefore is slightly green (Duv). \u00a0The Advanced Calculation Tool tells us that the R<\/em>9 value is 2 and that the R<\/em>f for skin is 85. \u00a0It also tells us the (x, y<\/em>), (u, v<\/em>), and (u’, v’<\/em>) chromaticity coordinates (which, frankly don’t mean anything to me, but the information is there). \u00a0This information is immediately useful and isn’t provided as part of the CRI calculation. \u00a0In addition, most light source manufacturers don’t tell us the Duv, although understanding it is becoming increasingly important, especially now that NEMA has extended the chromaticity bins for LEDs in ANSI\/NEMA C78.377<\/a> American National Standard for Electric Lamps – Specifications for the Chromaticity of Solid-State Lighting Products<\/em>. \u00a0That’s a post for another time.<\/p>\n

As I’ve already discussed, IES TM-30’s color fidelity metric R<\/em>f provides us with as little, or as much, information as we want. \u00a0If you just want top line information that the beige office you’re lighting will continue to look beige, you can have it. \u00a0An R<\/em>f of 78 is probably just fine. \u00a0If you want to see the fidelity of each of the 16 hue bins because you’re interested in the fidelity of a particular color range, it’s there. \u00a0If you want to know the R<\/em>f value of all 99 color samples you can have that, too! \u00a0What else? \u00a0Well, would you like to see the chromaticity coordinates in (x, y<\/em>) color space, the SPD vs the reference source, or a pictorial comparison of each of the 99 CES? \u00a0No problem.<\/p>\n

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

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

Pretty pictures but are they useful? \u00a0Not as useful as the data given above, but lighting designers do like to see this information, even if it’s difficult to interpret. \u00a0The CIE 1931 (x, y<\/em>) color space isn’t perceptually uniform, so the distance we see between the reference source and the test source isn’t very informative. \u00a0Seeing the SPD is interesting, but no one can read an SPD and know what the light looks like or how it renders colors. \u00a0The CES Chromaticity Comparison is also interesting, but the red and black dots aren’t connected to one another. \u00a0With some light sources it’s easy to tell how they relate so we can see chroma and hue shifts, but as R<\/em>f drops and color shift increases it gets harder and harder. \u00a0What is<\/strong> useful are the next two graphics: the R<\/em>f value by Hue Angle Bin and by CES.<\/p>\n

\"\"<\/a>\u00a0\"\"<\/a><\/p>\n

Now we can see how individual color ranges are affected by the lamp in question. \u00a0This may be especially useful on certain projects were specific color ranges are present and need to be accurately rendered. \u00a0The individual CES scores useful for the same reason. \u00a0However, in my opinion if you want information at that level of detail you’re probably better off doing a mockup and looking at project specific color and material samples instead of the CES.<\/p>\n

TM-30 arms the lighting specifier with as much or as little information as needed on a particular project. \u00a0It also provides additional information that may be important (such as Duv). \u00a0It then allows the specifier to apply experience and knowledge about the client and the project to determine whether or not a given light source is appropriate. \u00a0 \u00a0Who could say no to that?<\/p>\n","protected":false},"excerpt":{"rendered":"

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 provides us with a single … Continue reading TM-30 Rf: So Big, So Strong, So Smart!<\/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":[12,18,17,19],"tags":[27,68],"class_list":["post-787","post","type-post","status-publish","format-standard","hentry","category-color","category-design","category-light","category-lighting-profession","tag-color-rendering","tag-tm-30"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p4gZSw-cH","jetpack_sharing_enabled":true,"jetpack_likes_enabled":true,"jetpack-related-posts":[{"id":780,"url":"https:\/\/designinglight.com\/?p=780","url_meta":{"origin":787,"position":0},"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":491,"url":"https:\/\/designinglight.com\/?p=491","url_meta":{"origin":787,"position":1},"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":787,"position":2},"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":803,"url":"https:\/\/designinglight.com\/?p=803","url_meta":{"origin":787,"position":3},"title":"TM-30 Rg, The Gamut Index","author":"Jason Livingston","date":"December 4, 2017","format":false,"excerpt":"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\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\/12\/CVG.png?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2017\/12\/CVG.png?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2017\/12\/CVG.png?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":386,"url":"https:\/\/designinglight.com\/?p=386","url_meta":{"origin":787,"position":4},"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":617,"url":"https:\/\/designinglight.com\/?p=617","url_meta":{"origin":787,"position":5},"title":"IES Symposium Summary","author":"Jason Livingston","date":"April 6, 2016","format":false,"excerpt":"If you missed IES Research Symposium III Light + Color you missed an exciting (for color geeks) few days. It would take too long to relate everything that was discussed, but here are some key highlights. TM-30-15 is seeing broader acceptance throughout the industry. In an exciting development, it seems\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\/787","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=787"}],"version-history":[{"count":1,"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/posts\/787\/revisions"}],"predecessor-version":[{"id":793,"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/posts\/787\/revisions\/793"}],"wp:attachment":[{"href":"https:\/\/designinglight.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=787"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/designinglight.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=787"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/designinglight.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=787"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}