Tag: TM-30

Tony and I Talk Color Rendering

Podcast Album Cover

In September at ArchLIGHT Summit, Tony Esposito and I gave a series of demonstrations on the spectral flexibility of LEDs and the possibilities they present with regard to color rendering.  While there we spoke to Sam Koerbel on his LytePod podcast about the basics of the new measures introduced in Annex E, and discuss why TM-30’s multi-dimensional approach to quantifying color preference is superior to the old-standby in the industry: CRI.  Our discussion is now available.  Give it a listen.

The Strength of TM-30

Last week Tony Esposito and I presented seminars at ArchLIGHT Summit in Dallas, TX. The topic was TM-30 and the deep information that it provides us about a light source’s spectrum and the resulting color rendering. CRI, of course, only evaluates fidelity – how close a light source matches its reference light source. But CRI penalizes all deviations and says nothing about the rendering of individual colors. Nor does it help us understand if the deviations from the reference are acceptable to viewers.

A small part of our demo is shown below. It illustrates how two light sources can have the same fidelity (in this case Rf of 70) but wildly different spectra that produce wildly different color rendering results. This is the great strength of TM-30, a deeper insight into the effect of a light source on illuminated objects and their color appearance – not just fidelity, but chroma shift, hue shift, and the perceptual implications of those shifts.

The video below shows the color appearance shifts. The graphic illustrates that even though the Rf is 70, the first light source renders objects in a preferred manner (Preference Priority Level of 3 or P3) and increases vividness (Vividness Priority Level of 2 or V2). At the same Rf the second source mutes colors and fails to achieve any of the Design Intents and Priority Levels specified in TM-30’s Annex E.

Alternating between light sources with Rf 70, Rg 94 and Rf 70 Rg 111

TM-30 at ArchLIGHT Summit 2021

My colleague Tony Esposito and I will be giving a new TM-30 seminar and demonstration at ArchLIGHT Summit 2021 in Dallas on September 21st and 22nd. We’re working on a new, and we hope more attendee friendly, presentation and an all new set of demonstrations to explain TM-30s Annex E specifications. The demo will include, for the first time, live models of different ethnicities so attendees can evaluate the impact of of the specifications on skin tone. I hope to see you there!

TM-30 Is Not Too Hard To Learn!

Recently, a well-known lighting designer gave a presentation at a well-known lighting conference. During the Q&A he was asked his opinion of TM-30 and replied that it was too hard so he just specified CRI>90. At the risk of sounding like a jerk I have to say that maybe it was too hard for him, but it’s not too hard for most of us. Here is a brief list of new things lighting designers have had to learn over the years.

  • The introduction and transition to electronic ballasts and transformers meant that we had to learn about reverse phase dimming and control protocols.
  • The T5 lamp meant we had to change our layout patterns to accommodate lamps that weren’t standard 2’, 4’, and 8’ lengths.
  • Metal Halide lamps, especially PARs, meant that in exchange for energy savings we had to learn about the color rendering of a new type of lamp, and give up dimming.
  • Daylight harvesting and daylight responsive designs meant we had to learn about daylight zones, photosensors, and daylight harvesting control systems.
  • White LEDs meant we had to learn about another light source and its specific pros and cons, including different color rendering properties due to its SPD.
  • Circadian lighting means we are all in the process of learning how and when to apply the most current scientific evidence to certain project types.  Since the science is constantly advancing on this topic, we must be aware and continue to educate ourselves.
  • Regularly updated energy conservation codes mean that as we begin to memorize the lower LPDs and changes to control and daylighting requirements, we have to relearn that information because it changes every three years.
  • Most recently, we’re supposed to enthusiastically embrace IoT, adding new hardware and controls to our lighting control systems.

There is a ton of TM-30 educational material available, including posts on this blog here, here, here, here, here, and here. There’s this article on the IES’s FIRES Forum, and this page on the Department of Energy web site. Manufacturers are also providing education including DMF Lighting, Soraa, Premier Lighting, Alphabet, and Lighting Services Inc. Then there are the articles in trade magazines and sites such as Lux Review and Architect Magazine, not to mention many articles in Lighting Design and Application and Leukos (no links because they’re behind the IES login). In addition, there have been presentations at other conferences (some given by me) at the IES Annual Conference, LightFair, and LEDucation.

If that’s not enough for you, let me know. I have a presentation approved for one AIA HSW LU, so if you’re architectural firm wants to learn more let’s set up a presentation. Ditto for lighting design firms and teachers of lighting. If I’m not available there are a half dozen others on the IES Color Committee who regularly give TM-30 presentations. You can learn TM-30. I’m here to help.

Standard 189.1 Now Includes TM-30 Requirements

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:

8.3.5.3 Color Rendition. At least 95% of lighting power of nominally white lighting within each enclosed space shall be provided by luminaires that meet the following criteria at full light output in accordance with IES-TM-30, Annex E, P2 and F3:
1. Rf of at least 85
2. Rf,h1 of at least 85
3. Rg of at least 92
4. Rcs,h1 of at least -7% but no greater than +19%

Nominally white lighting is lighting that has chromaticity within the basic or extended nominal color correlated temperature (CCT) specifications of ANSI C78.377.

Where a lighting system is capable of changing its spectrum, it shall be capable of meeting the color rendition requirements within each nominal CCT of 2700 K, 3500 K, 4000 K, and 5000 K, as defined in ANSI C78.377, that the system is capable of delivering.

I hope that this is going to put more pressure on manufacturers to improve the color rendering of their luminaires as measured by TM-30, not CRI, and to provide TM-30 information on their cut sheets. If not, they’ll risk not being considered on projects that have TM-30 requirements.

LEDucation Postponed

Due to growing concerns of COVID-19 in the lighting industry and the New York community, the Designers Lighting Forum of New York is postponing the LEDucation 2020 Trade Show and Conference that had been scheduled for March 17 – 18.

LEDucation is being rescheduled to August 18 – 19, 2020. I expect that our TM-30 Annex E seminar and demonstration room will be part of the rescheduled event.

Using TM-30 to Improve Your Lighting Designs

Recently, ANSI/IES TM-30 was improved with the addition of Annexes E and F.  Annex F reviews and summarized five studies that explored using TM-30 metrics to predict subjective visual outcomes.  Annex E uses that research to establish recommended specification criteria when the designer’s color rendering goals are Preference, Vividness and/or Fidelity.

The IES Forum for Illumination Research, Engineering, and Science (FIRES) has an article I wrote with Michael Royer and Tony Esposito explaining the Annexes and how to use the information in Annex E.  Here’s the link: Using TM-30 to Improve Your Lighting Design – Illuminating Engineering Society

I’ve been using Annex E on projects and have spoken to other designers who have begun to use it.  It provides useful, accurate information that allows me to evaluate the color rendering results of light sources in a way that hasn’t been possible until now.  It lets me make informed decisions about my projects, and explain those decisions to colleagues and stakeholders in (relatively) easy to understand terms.

TM-30 and the TM-30 calculators continue to be a free download from the IES here.  Annexes E and F are also free on the Errata and Addenda page here and here.








Misunderstanding CRI

Last Friday I took my class on a visit to a fixture manufacturer’s showroom.  The visit was pretty successful, but I had one issue with the information that was presented.  This manufacturer’s rep presented their CRI 80 and CRI 90 products by saying that CRI 80 dulls colors and CRI 90 makes colors “pop”.  I can’t blame him too much, after all it’s a common misconception that higher CRI is “better.”  However, it’s not true so let’s take a look.

 CRI (or more formally, CIE 13, Method of Measuring and Specifying Colour Rendering Properties of Light Sources, Ra) is a fidelity metric.  That means it calculates the color rendering of a light source in comparison to the color rendering of a reference light source of the same color temperature or correlated color temperature (CCT).  A light source with a CRI 80 renders colors with more color error (that is, a larger mismatch or a larger color appearance distortion) than a light source with a CRI 90.  That’s all. One of the problems with CRI, which is addressed in TM-30, is that a single number value doesn’t tell us the hue(s) where there is a color rendering error compared to the reference light source, nor do we learn the direction or the degree of color rendering error(s).  In other words: 

  • What hues are not rendered accurately?  CRI doesn’t tell us.
  • Are those hues made to appear more or less saturated?  CRI doesn’t tell us.
  • Are those hues shifted toward an adjacent hue?  CRI doesn’t tell us.
  • How big are the color distortions? CRI doesn’t tell us.

 TM-30 (ANSI/IES TM-30-18 IES Method for Evaluating Light Source Color Rendition) does give us this information, which immediately puts to rest the notion that higher fidelity is “better” color rendering in all cases. 

It’s entirely possible for a light source with a CRI 80 to render a set of colors more vividly than a CRI 90 light source if the color errors increase saturation and minimize hue shifts.  It’s even possible for two light sources of the same CRI to render colors differently.  Here’s an example.  The first light source has a TM-30 Rf (fidelity) of 90 and an Rg (chroma) of 99, meaning that on average colors are rendered slightly less vividly than the reference light source.  The TM-30 Color Vector Graphic shows us clearly that the rendering of red (Bin 1) is less saturated than the reference, and that the rendering of warm blue (Bin 12) is more saturated.  The other colors are a nearly perfect match to the reference source.

The second source  also has an Rf 91.  However, the green and purple hues are rendered with increased saturation so that it has an Rg 105. (Yes, the CCTs are different, but that doesn’t matter because in the calculation a light source is compared to a reference light source of the same CCT, cancelling out any color errors due to CCT.) 

Understanding this information opens the door to considerations other than fidelity.  The first is vividness.  Are you lighting the M&M store in Times Square?  If so, your design goal may be to increase saturation of the candy, not accurately render it.  In that case you’re going to want a lower fidelity (Rf) so that you can get higher chroma (Rg).  The light source shown below might be just the one for this application.

 The second is preference.  Studies have shown that in many applications people prefer slight increases in chroma, especially in the red range.  Are you lighting a restaurant?  If so, and if preference and increased red chroma are important, this might be the light source for your project: 

The increased information TM-30 provides is both more accurate and more detailed than CRI.  Not only that,  it gives us a deeper understanding of the color rendering capability of a light source and allows us to consider design goals other than fidelity. Designers who care about these color considerations need to keep pushing manufacturers to provide TM-30 information and train their employees in its meaning and use.