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 link below takes you to a recent LD+A Online article I wrote with Michael Royer and Jess Baker, It addresses some of the issues related to LED color names, and explains the ways colored LEDs are described, including dominant wavelength, peak wavelength, and chromaticity coordinates.
You may recall that in 2019 the Trump administration blocked a rule intended to phase out incandescent lamps and encourage a conversation to more energy efficient models, namely LEDs. If you don’t remember the New York Times and NPR both had articles, among many others.
Last week, the Consumer Federation of America and the National Consumer Law Center, along with 24 other groups across the country, urged the U.S. Department of Energy (DOE) Secretary Granholm to implement the efficiency standard for household lighting products mandated by Congress as soon as is practicable. They claim that “Each month of delay costs American consumers nearly $300 million in lost utility savings and results in another 800,000 tons of climate changing CO2 emissions over the lifetimes of the incandescent bulbs sold in that month.”
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:
188.8.131.52 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.
Last Thursday Donald Trump spoke to a group of Republicans in Baltimore. One of the things he said caught my attention: “The lightbulb. People said what’s with the lightbulb? I said, here’s the story. And I looked at it, the bulb that we’re being forced to use, No. 1, to me, most importantly, the light’s no good. I always look orange. And so do you. The light is the worst.”
Now, I’m not aware of being made to look orange under LEDs, nor have I ever noticed LEDs making my friends, colleagues, or students appear orange. You can’t imagine how embarrassed I’d be if it turned out that a real estate developer and entertainer had more astute color perception than me, a lighting designer and Co-Chair of the IES Color Committee. If our only means of evaluating the color rendering of a light source, and evaluating the orange content specifically, was CRI we would have no objective way of testing his statement. CRI, technically Ra, is a single value that gives us an average of the match between the light source in question and its reference source (either a blackbody radiator or a CIE definition of daylight, depending on CCT) using only eight color samples.
Since Ra is an average value there’s no way to understand the rendering of any particular hue. I’ve talked about this here. However, one of the wonderful things about ANSI/IES TM-30 IES Method for EvaluatingLight Source Color Rendition is that we can use it to test that claim. TM-30 uses 99 color samples that are distributed across the color space and the visible spectrum.
It also breaks the color space up onto 16 Hue Bins, each one covering a specific range of the color space. In the case of orange, we want to look at Hue Bin 3. Specially, we want to look at Rcs,h3 (the subscript CS stands for Chroma Shift) which quantifies the increase or decrease in the saturation or vividness of orange compared to the reference light source.
So, let’s put the science of TM-30 to work and see if we really do know that LEDs make us look orange!
The TM-30 calculator contains a library of 300 SPDs (spectral power distributions), of which 137 are commercially available white LEDs. The CCTs range from 2776 K to 6123 K. If white light LEDs really did make us look orange we’d expect to see a large majority of them have a positive Rcs,h3, probably with an average chroma shift in excess of 10%. In fact, the 137 SPDs have Rcs,h3 that range from -8% to 1% with an average of -3.6%, a decrease (not an increase) in the saturation of orange. It’s not me, it’s him. TM-30, which uses the most modern models of human vision and a set of colors that cover the color space and visible light spectrum, proves it. What a relief!
Don’t believe me? Download TM-30 and the calculator for free from the IES web site and see for yourself.
Of course, I’m not saying LEDs are perfect light sources. Like any other product there are good ones and bad ones. However, TM-30’s measurements of fidelity and gamut (as averages) and measurements of fidelity, chroma shift, and hue shift (by hue bin) permit us to make a thorough evaluation of a light source to understand its color rendering characteristics. Using this knowledge, we can determine if a particular light source distorts colors and is appropriate for a project, or not.
I should take a moment to note another error he made when he said, “And very importantly—I don’t know if you know this—they have warnings. If it breaks, it’s considered a hazardous waste site. It’s gases inside.” Perhaps you’ve heard the acronym SSL or the phrase solid state lighting. LEDs are a version of SSL, which means that they are…well, solid. Unlike previous light producing technologies LEDs are a solid combination of materials. As such, if one were to physically break (which is unlikely since LEDs are small, are mounted to a heat sink and often covered with a lens, so you’d have to break a lot of materials simultaneously) no gas, hazardous or benign, is emitted. He’s thinking of fluorescent lamps and the small amount of mercury they contain. Even then, a broken fluorescent lamp doesn’t turn the area into a” hazardous waste site.” Here are the EPA’s instructions for cleaning up a broken fluorescent lamp.
In 2007 Congress passed the Energy Independence and Security Act (EISA) with the goal of increasing energy efficiency across the economy. Part of EISA has affected the lighting industry in the form of mandated efficacy of light sources. The initial efficacy rules targeted A-Lamps (standard household light bulbs) and set the efficacy level above that of incandescent but below that of halogen lamps. The result was a slow shift to the more energy efficient technology. Over the years the energy efficiency requirements have been expanded to more lamp shapes, always in keeping with technological ability so that we never faced a lamp shortage or loss of a lamp shape. Today, more than 50% of lamps sold are LED that exceed even the most stringent requirements.
On September 4th the administration announced that it was going to cancel a new set of requirements that would have taken effect in January 2020 that would have applied to products such as decorative medium base lamps and MR type lamps. In my opinion, this is another example of the administration cutting off its nose to spite its face. As with the threat to “investigate” automakers who agree with the State of California’s proposed energy efficiency requirements, this effort to undo energy efficiency despite the monumental consensus that we need to reign in our energy consumption isn’t going to go have any effect. No lamp manufacturer is going to reopen or build new factories to make incandescent lamps when it’s obvious that A) the next administration is going to reinstate the efficacy requirements B) the public has embraced the energy savings of LED lamps, and C) the companies know that it would be bad for their image to turn their backs on mitigating climate change.
An interesting bit of news from Samsung this week. They’ve developed an LED package especially designed to achieve an Rg value over 110, “a level that ensures lighting with outstanding color and whiteness.”
It’s important to note that increased saturation means decreased fidelity to the reference light source. This is a lighting solution that will be desirable in some applications, such as retail,and undesirable in others, such as medical facilities.
is inadequate for the purpose of evaluating possible health outcomes; and that the recommendations target only one component of light exposure (spectral composition) of what are well known and established multi-variable inputs to light dosing that affect sleep disruption, including the quantity of light at the retina of the eye and the duration of exposure to that light. A more widely accepted input to the circadian system associated with higher risk for sleep disruption and associated health concerns is increased melanopic content, which is significantly different than CCT. LED light sources can vary widely in their melanopic content for any given CCT; 3000 K LED light sources could have higher relative melanopic content than 2800 K incandescent lighting or 4000 K LED light sources, for example.
Follow the link to read the entire Position Statement. Blue light hazard, light’s impact on circadian rhythms and overall health, and related topics are a hot area of research. We’re learning more all the time, but we don’t yet know enough to apply circadian lighting to every situation. Outdoor and street lighting are among the areas where research is not yet conclusive.
Like other lighting technologies, the color or chromaticity of light emitted by an LED can shift over time. To address the challenge of developing accurate lifetime claims, DOE, together with the Next Generation Lighting Industry Alliance, formed an industry working group, the LED Systems Reliability Consortium (LSRC). A new LSRC report, LED Luminaire Reliability: Impact of Color Shift, focuses on chromaticity. The purpose of the new report is not to define limits for specific applications, but rather to enable a better understanding of how and why color shifts, and how that impacts reliability. Download it and take a look.
In the lighting community there was a considerable amount of frustration and anger over the report for several reasons. First, there were quite a few references cited that were either hearsay, such as a New York Times article about Brooklyn residents who didn’t like their new LED street lights, or were irrelevant, such as several articles about the effect of skyglow on nesting turtles. The other reason was that there was not a single lighting designer or researcher on the panel. Overall, it was a poorly researched paper that didn’t deserve the attention it received.
Shortly after it was issued, the Lighting Research Center at RPI issued a response paper. On March 15 the authors of that paper held a webinar to further address the AMA report. A video of that webinar is now available. If you’ve got an hour, take a look.
The key takeaways regarding the hazard of blue light from LEDs and the report are:
The criteria of blue light hazard for retinal damage is much more than just color temperature, and includes the source size, intensity per unit area on the retina, and SPD of the light source.
Disability glare is not a function of light source SPD, as the AMA paper suggests, although discomfort glare is. Short wavelengths increase discomfort glare.
Color temperature is the wrong measurement to determine whether or not a light source will affect the circadian system and melatonin production because color temperature does not provide complete SPD information. For example, some 3,000 K LEDs can have a greater impact than 4,000 K LEDs.
The criteria of blue light hazard for circadian disruption from a light source include – the intensity, duration of exposure, timing of exposure, and SPD.