Color Rendering, Whiteness, and TM-30

I know I often write about color rendering. It’s because most lighting manufacturers and specifiers treat color rendering as a check box item (80 or 90?). I see color rendering as a powerful, valuable design choice that impacts the appearance of a space. This is especially true when using TM-30’s suite of measurements. So, here I go again…

I recently came across an ad from a luminaire manufacturer that described three versions of a new product line that focuses on color rendering. One version is supposed to “enhance the contrast between colors and whites”. Another is supposed to “accent wood, bronze, textiles and darker accents” (so, warm colors, all colors, and dark colors?). The third is supposed to “enhance white surfaces”. All three versions are described having a CCT of 3000 K and a CRI of 90, and that’s all we’re told. There is no other color rendering information presented in the ad, on the web site, or on the cut sheets. It’s as though somehow 3000 K and 90 CRI are supposed to clearly describe all three color rendering effects. CRI – it’s a hair gel, it’s a toothpaste, and it’s a floor polish! Obviously, this is nonsense. So, let’s talk about what’s really going on here.

Over the years CRI has been erroneously described as measuring the naturalness of a light source, the naturalness of colors, a comparison to daylight, and even a percentage of colors that are rendered (whatever that’s supposed to mean). All of those are wrong. CRI is a fidelity measurement. That is, it compares a light source to its reference source (a black body radiator below 5000 K and a model of daylight at 5000 K and above, and at the exact CCT as the light source in question) and describes how well they match. The reference light source isn’t meant to be considered perfect – it’s meant to be a light source with well understood color rendering properties. A poor match in color rendering results in a low CRI. A better match results in a higher CRI. A CRI of 90 indicates a pretty good, but not exact match. What is the mismatch? What specific colors or color ranges are affected? Are some colors shifted in hue, made less saturated, made more saturated, some combination? We don’t know the answers because the CRI calculation gives us one number, R_a, not a suite of numbers and/or graphics that supplement the top line result.

So, a light source that is 3000 K and 90 CRI might have one of the three color rendering properties described by this manufacturer, and other versions of 3000 K and 90 CRI could have the other characteristics, but the numbers presented don’t describe or confirm those properties or characteristics at all. For that we need to look at TM-30 and beyond.

Two of the three descriptions reference the color rendering of white, but there’s no explanation of how this is determined, and that’s a problem. Neither CRI nor TM-30 specifically evaluate white surfaces or materials. There have been several whiteness metrics proposed over the years, beginning in the 1930s. As far as I know, only one has been adopted by a standards setting organization (the CIE whiteness formula from 1986). However, this manufacturer can’t be using the CIE formula because it only uses D65 (a standardized spectra at 6500 K) and the LEDs here are all 3000 K.

Neither CRI nor TM-30’s R_f (the fidelity index) say anything about the impact of the spectrum on specific color ranges, such as warm colors. R_g doesn’t either since it gives us an average shift in saturation across all 99 color samples. To see what color ranges are affected, and how, we need to look at the local hue and chroma shifts (“local” meaning the color samples falling within each of the 16 hue bins shown in the Color Vector Graphic or CVG). As shown below, a TM-30 intermediate report gives us the CVG and bar graphs of the hue shift (R_hs) and chroma shift (R_cs) for each hue bin. The bar graph information is included in the Color Vector Graphic, of course, but some may find the bar graphs easier to read.

So, if the question is, “What colors are enhanced by this spectrum?”, and if “enhanced” means made more vivid, the answer is found in the chroma shift bar graph. For any spectra, the color ranges that have a positive chroma shift would be enhanced, while those with a negative chroma shift might be described as being muted, dulled, or grayed. This is true regardless of the material because color rendering is about an object’s color, not its material composition. “Textiles and darker accents” don’t describe a color range, so there’s no way of knowing the impact of a spectra on those materials without also knowing their color. As with whiteness, though, the manufacturer gives us no detailed information, just assurances that these lights are great.

Proceed with caution. Don’t accept any of these claims without proof. Get your lighting reps to bring you samples to evaluate before specifying these products. CCT and CRI cannot explain and back up a claim about a light source’s impact on the appearance of specific color ranges and white materials. To do so, a manufacturer should provide specifiers with a description of the impact, a TM-30 report that supports that claim, and perhaps additional metrics for claims that can’t be verified or validated with TM-30.

False TM-30 Reports

I recently received a set of lighting submittals. In them, one manufacturer had included TM-30 Full Reports. At first I was delighted, thinking, “Finally, a manufacturer who’s made TM-30 a default part of their documentation!” Here’s the report.

false tm-30 report

My excitement was followed, a few seconds later, by a sinking feeling as I realized that the report was falsified and was a composite of at least two SPDs. Can you spot the errors?

The first odd item is the gray boxes around each graphic. Neither the Excel calculator nor the online calculator have those boxes as part of their graphics. Something’s wrong.
Look at the CVG and notice that the red shape, which represents the color rendering of the test source, very closely matches the black circle, which is the reference light source. This is the hallmark of a high fidelity light source, and we would expect both Rf and Rg to be near 100. Why is Rf 91? Should it be higher?
Look at Hue Bin 1 (red). Notice that it’s almost touching the reference source circle. There’s almost no hue shift or chroma shift. But…
Look at the graph of Local Chroma Shift. Hue Bin 1 has a chroma shift of -12%, yet the red shape in the CVG is nearly touching the reference light source and is nowhere near the -10% white ring. These two graphics are not from the same SPD.
Likewise, the Local Color Fidelity of Hue Bin 1 is 80. Again, the CVG shows almost no hue or chroma shift, so the Rf should be much higher than 80. These are not from the same SPD.

What’s happened? I honesty don’t know. Obviously, someone cut and pasted TM-30 report components from at least two SPDs to create a false report – there’s simply no way the calculator created this from a single SPD. Was it done out of ignorance or for a purpose? Well, there’s no reason to cut and paste elements of a report because they’re generated automatically by the calculator. I don’t know why this one was edited. I do know that I rejected all fixtures by this manufacturer in this submittal. I noted that if I they’re falsifying the spectral data I have no reason to believe they’re not doing the same elsewhere – driver into, housing dimensions, CCT, beam angle…who knows what they’re going to ship?

Where are the Photometrics?

Today I want to talk about the lack of photometric information provided by manufacturers because the presentation of information frustrates me in two ways. The first issue is the lack of information provided. The second is the difficulty of finding real world examples of what I teach in class. What’s the value of knowing the point and lumen methods if the information needed isn’t available? It seems to be a problem that’s getting worse and I’m not sure why.

Do manufacturers not understand photometric calculations, so they don’t see the value in including them?
Do manufacturers think lighting designers don’t understand photometrics, so they don’t bother including them?
Do manufactures not understand how lighting designers work, and think all calculations are done in AGI? I suspect this is the answer.

By failing to publish photometrics, manufacturers are dictating my workflow without understanding how I work and why I work the way I do. I rarely name names, but I’m going to make an exception here. Maybe a little photmetric-shaming (one of the most obscure types of shaming, to be sure!) will get manufacturers to change.

Are You a Contender?

When I navigate my way to a fixture web page and open the cut sheet my main goal is to determine if the fixture is a contender. Does it seem to have the features I’m looking for? If not I can move on. If so, the next question is, “Does it have the performance I’m looking for?” Photometrically, I’m looking for general distribution type, followed by more specific distribution information, lumen output and load, and beam angle. If those look good, I’ll scroll down the cut sheet to the photometric section to get some info to run a quick calculation in a spreadsheet that’s open on my desktop. If the fixture works in that quick calculation I’ll download the cut sheet and .ies file and run an AGI calc when I’m ready. What I’m looking for on the cut sheet, depending not the calculation, is:

Lumen output
Center beam candlepower
Beam angle
Candelas distribution
Coefficient of utilization (CU) table

For example, I recently went looking for a linear downlight. My first stop was Coronet because I know they’ve recently revamped their historically deficient cut sheets. Are the new cut sheets any better? No. The first page of the cut sheet for the LSR2, for example, now has a section labeled “Optics” (not photometrics) and gives a sort of candlepower distribution curve, but there’s only one number, which seems to be candlepower at nadir but isn’t labeled as such. A separate section at the bottom of the next page shows “Performance” in terms of watts/ft and lumens/ft for three output levels. That’s it. Any reasonable calculation of the fixture’s performance in a space requires downloading .ies files, building a model in AGI, and running a calculation. As I said earlier, that’s not my workflow. I can run a lumen method calc much faster than I can build an AGI calc and I don’t want to be forced into AGI.

Next I looked at Focal Point’s Seem 2. As with Coronet, there’s a candlepower distribution curve. The ordering matrix tells me there are four lumen outputs, and there’s a table of output, watts, and lumens/watt. A lot of page space is given to lengths and controls, but there’s nothing else about photometric performance on the cut sheet. To find any useful information I have to download .ies files and open them in Photometric Toolbox or AGI.

Finally, I looked at Acuity’s Mark Lighting. The cut sheet for the Slot 2 LED presents a table of lumens/ft, watts/ft, and lumens/watt for four output levels, but there’s no candlepower distribution curve or CU table. On the plus side, the information I want is provided, but in a separate location on the web page called Photometry & Revit (BIM). If I click on Report I find a polar candelas graph, zonal lumen summary, CU table, etc. I wish this was in the cut sheet, but at least it’s available.

I have similar complaints about other manufacturers who make fixtures I generally like: Alphabet, USAI, Day-O-Lite, and Ecosense among them.

Let Manufacturers Know

If you’re similarly frustrated let manufacturers know. If you’re at Lightair this week tell them face to face. If not, tell your reps and anyone at the factory you may know.

IES RP-16 is Now IES LS-1

The Illuminating Engineering Society’s Recommended Practice 16 Nomenclature and Definitions for Illuminating Engineering (aka RP-16) has long been one of the two reference sources for the definition of lighting related words and phrases – the other being the CIE International Lighting Vocabulary (ILV).

As part of the IES converting all of their publications to an online library format, some publications have been given a new designation. RP-16 is now Lighting Science 1 (LS-1) and is at this link. Bookmark it now!

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. R_f of at least 85
2. R_f,h1 of at least 85
3. R_g of at least 92
4. R_cs,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.

Fixture Cost Frustration

One of my clients has expressed frustration with the caveats I place at the end of my lighting fixture budget. Why can’t I give the client a simple budget estimate? The answer is that fixture manufacturers don’t have a manufacturer’s suggested retail price (MSRP) for their products, which is something we’ve all come to expect for products ranging from potato chips to cars. We all know that things we want to buy have an MSRP or list price and it’s up to the seller to decide whether or not to sell at a lower price.

However, with lighting equipment the sales representative and the manufacturer collaborate to establish pricing for each project (see chapter 9). Larger projects with more luminaires will usually pay less per luminaire. This can be frustrating for everyone. It’s hard to develop a reliable fixture cost database when fixture costs are variable.

Another issue with pricing from the sales rep is that it is usually dealer net, distributor net, or DN pricing. This means that the luminaire price the sales rep gives to the designer is the price that the electrical distributor will pay the manufacturer. It does not include the electrical distributor’s markup for overhead and profit, nor does it include possible markups by the electrical contractor and/or the general contractor. It is up to the lighting designer to estimate the total markup(s) as well as taxes, shipping and such, and add that amount to the projected lighting fixture budget, but designers have no direct knowledge of what markup these firms will add, nor do we have any control over their markups. The result is that I wind up footnoting my budget with notes like markup percentages are estimated, pricing is based on cost estimates provided by sales representative, and pricing is based on projects of similar size and scope.

Finally, as I explained here, the fixtures that I specify may not be purchased for the project. Once substitutions enter the picture another layer of mystery is added. Yes, it’s complicated. Here’s a flow chart that tries to explain the flow of information (denoted by question marks) and money (denoted by dollar signs) of design and sales relationships. See chapter 9 for a full explanation.

Substitutions vs Specifications

Earlier this week I had a disagreement with a contractor about my specifications and fixture schedule. The client, who had never been involved in a construction project of this type, didn’t know which one of us to believe. It went like this: We are coming up on the end of construction and the contractor is slightly over budget. In order to save money he wants to start to substitute less expensive products for those that have not yet been purchased which, in this case, includes the lighting fixtures and control system. His problem is that my specification and fixture schedule are so clear and precise (also referred to as “tight”) that he is having a hard time finding acceptable alternates. He told that owner that my tight specification is unfair because of this, and that I’ve essentially “given” the project to certain manufacturers “regardless of price.” I explained that a tight specification protects the integrity of the design, and thus protects the owner, by guaranteeing that the expected design is the one that is installed. Who is a client to believe? Let’s go through this.

As a lighting designer I have one source of income – my fee. I don’t get a royalty or commission from manufacturers that I specify*, I don’t sell fixtures to the project, and I don’t set pricing for fixtures. As a result, my only incentive to specify one manufacturer over another is appropriateness for the project. I talk to the owner about their needs and desires, budget, and timeline. I evaluate fixtures based on performance, options, accessories, quality, and price. I run calculations to make sure that the appropriate amount of light is being delivered and that the lighting system’s power consumption is within code limits. In some cases I’m contractually required to identify three equal fixtures for each type. That’s a lot of work and I want to make sure that it isn’t lost or undermined, so I write a tight specification.

After all of that work, though, most projects don’t require the contractor to provide only those items that the designers have specified. The rationale is that this gives contractors more flexibility in getting the best price, especially for public projects being paid for with tax dollars. In practice, however, this is often not the case. The contractor wasn’t present during the design process and doesn’t understand the criteria that went into selecting each fixture. He (or she) is primarily concerned with price, not performance. It’s common for the first round of substitutions offered by the contractor contain a large number of fixtures that are inappropriate for one reason or another. If a substitute fixture will do the job I usually accept it, but I won’t accept a fixture just because it’s offered. A tight specification sets the requirements for the fixtures and provides the basis for rejecting inappropriate substitutions. Yes, this can constrain the contractor’s choice of substitutions but for a good reason. There are huge variations in fixture performance, even when fixtures look the same. I’ve had contractors (and architects) say that a downlight is a downlight is a downlight. Take a look at the photometrics and it quickly becomes obvious that this just isn’t so.

From a designer’s perspective we protect the client by protecting the design, accepting substitutions that work but rejecting those that don’t. A tight specification can limit the amount of back and forth with substitutions by setting strict criteria that substitutions must meet. That’s part of the professional expertise we bring to the project.

*I admit I do sometimes get a nice box of chocolates during the holidays.