Goodbye CRI, Hello?

You may have heard that the CIE (International Commission on Illumination) has finally agreed with numerous illumination and color of light experts to abandon the Color Rendering Index (CRI) method of measuring the quality of white light. That was the easy part (not really, it took a long time, but stick with me.)

While those of us who simply want to specify and use good light have referred to this characterization as CRI, the CIE calls it R_a, CIE General Color Rendering Index. They are recommending a replacement with R_f, CIE General Color Fidelity Index.

When we lived in an incandescent and fluorescent world, CRI worked fine. As we started to employ more fluorescent and then a total LED replacement, the known flaws in the CRI system became more and more apparent. Something different was needed. Early on, the CIE admitted that CRI was not acceptable, but was noncommittal on a replacement. This world organization is known for its detailed deliberation. When it makes a decision, it comes with a lot of weight.

Over the years, a number of replacement concepts were proposed and rejected until the lighting community was presented with TM-30. While there were a few objections, most everyone agreed this was a superior metric. Much of the commercial lighting industry has already begun using TM-30. We decorative lighting folks have maintained an allegiance to CRI for very clear reasons. It was easy. 100 = good; zero = bad. If we’re close to 100, we should be satisfied. Besides, we have just begun to take light quality seriously, some slack was needed to be given to those of use less technically inclined.

One reason TM-30 is so fully supported is because it is actually two different measurements packed into one metric. There is a one-for-one replacement for CRI or R_a. That is R_f (fidelity.) It also measures color saturation and that portion is call R_g (gamut.) The CIE also recognizes that a single fidelity measurement does not tell the whole story. They are setting a foundation for a more comprehensive metric that could be TM-30, or could be something else.

What Can Decorative Lighting Expect?

I understand change is hard. I was around when decorative manufacturers, retailers and the design community needed to digest a new set of data points. Color Temperature and CRI were rarely discussed and poorly understood prior. Nonetheless, we all rose to the occasion. Here’s what we should expect to see in the coming months and years.

Timing	Metric
The past and currently	CRI	We may see many decorative manufacturers cling to the old measurement
Coming Soon	CRI + Rf	To help in the transition, showing both numbers will help users understand the number and the benefits of change
Future	Rf	With the term an integral part of the dialog, CRI can then be eliminated
The Desired Future	Rf + Rg (?) / TM-30 / ?	Everyone understands we need a more comprehensive metric. Will TM-30 be the answer, or a stepping stone to something else?

I don’t know how long it will take for the decorative lighting world to see this change, but I do know, TM-30 was adopted a lot faster than I had expected in the commercial space. For that reason, I urge you to take a minute or two and understand what could be coming your way. Remember when you were the only one who understood CRI? That time is coming again.