Are We About to Replace CRI?

Post by on September 11, 2015 in Lighting Tips

CRI Chart

The original 8 CRI chips with the enhanced R9-R14 additions.

On Sept 15th the IES and DOE will jointly present a new standard for evaluating color rendition from light sources. The standard is called TM-30-15 and depending on who you read, it will either radically change the lighting world or be yet another attempt at improving on the outdated and uninformative CRI standard. Ahead of the webinar (and honestly if you care at all about lighting you should sign up) here’s what we know and don’t know about the new metric. Also, at the outset I should admit to you all that I am borrowing heavily from the terrific reporting done in Architectural Lighting on this subject.

Here’s What We Know

It’s fair to call TM-30-15 an evolution from CRI and CQS. The color quality scale moved us from 8 colors to 15 and included more saturated hues giving us the often discussed “R9” value as a way to measure true red in an LED source. Despite some improvements, CQS never took off as a standard industry wide.

TM-30-15 Test Chart

The new 99-color chart used in TM-30-15 testing

The basics of the new test are out there – now a given light source will be tested not to 8 or 15 colors, but a full 99 colors ranging from pastels to saturated hues. In addition to the added colors for testing, a light source will be given two scores one for fidelity (Rf) and another for gamut (Rg). The Rf score is similar to CRI as it maxes out at 100. The Rg score can be above 100. The idea here is to give you an idea of both how well a color can be recognized under a given light source and how much it over or under saturates colors.

This is explained well in the Architectural Lighting piece:

Similar to CRI, an Rf of 100 indicates a perfect match with the reference. Rg is calculated by plotting a light source’s chromaticity values in a color space and comparing the area to that of a reference source. “If Rf is 100 … Rg must also be 100,” wrote New York–based Studio T+L principal and IES Color Committee member Jason Livingston on his website, Designing Light. “As the Rf value falls, the potential range of Rg above [or] below 100 (indicating an increase or a decrease in saturation) grows.”

What We Don’t Know

For all that we do know about the new standard, what we don’t know is how rapidly the industry will take to it. Manufacturers have optimized (some would say gamed) their light sources to achieve 90+ CRI and they may be loathe to test to a new more rigorous standard. As with previous attempts at improved color rendition scales there might also be push back if the new testing diminishes the value of products previously boasting high CRI scores.

My guess (and that’s all it is) is that with the department of energy standing behind this testing standard there is a much higher probability that this standard will make it’s way into broader lighting guidelines and perhaps even laws (like the 90+ CRI requirement for sources in California). Basically, it just feels like this standard is going to get more traction with the IES and DOE and therefore the industry is going to come to heel. Of course, I could be wrong.

We’ll know a lot more about the rollout after the September 15th webinar and we’ll share what we learn then…

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