July 7, 2025
Beyond CRI & TM-30: Why Tunable LEDs Need CRV
A new measure shows how many spectral mixes make the same white light
For decades, lighting quality has been judged by how faithfully a source reveals colors. First came the trusty CRI. Then TM-30 arrived in 2015 to fix its flaws. Both ask the same question: How well does this light render colors—right now, at this setting?
But what if the light doesn’t stay the same?
That’s the question behind a new metric that recently landed in LEUKOS, the journal of the Illuminating Engineering Society. Developed by Michael Royer and Douglas Baxter of Pacific Northwest National Laboratory (PNNL) and Alp Durmus of Penn State University, Color Rendition Variability (CRV) is not another version of CRI or TM-30. It’s something else altogether—a tool built for the new reality of tunable, multi-primary LED systems.
One White, Many Spectra
Here’s the dilemma: A basic white LED—like the steady 3000K lamp above your kitchen island—has a single, fixed spectrum. Its color rendering can be measured once with CRI or TM-30. End of story.
But modern tunable lights, packed with three, four, sometimes even seven or more varieties of LEDs—red, green, blue, amber, lime—can hit the same shade of white in dozens or even millions of different ways. These spectral tricks, called metamers, fool the eye but change everything about how colors look on objects.
A museum curator tweaking a spotlight might use this flexibility to make a painting’s reds richer without changing the gallery’s ambient white. A retailer might tune fixtures so drab winter coats look vivid under the same CCT that made colorful swimsuits pop in summer. A hospital might tune spectrum for circadian comfort, all while keeping the white steady to the patient’s eye.
Until now, designers had no good way to quantify just how much wiggle room a tunable fixture really had. CRV aims to fill that void.
So What Exactly Is CRV?
In simple terms, CRV measures how many distinct ways a tunable, multi-primary LED system can render colors—without shifting away from a target white point. As Royer’s team puts it: “CRV quantifies the extent to which a multi-primary product can vary color rendition within a defined set of parameters.”
In practice, that means taking all the possible spectral mixes that can produce a single chromaticity—same white, in other words—and counting how many unique combinations give meaningfully different color rendition scores for fidelity, gamut, and hue boost.
The result is a percentage: higher CRV means more flexibility to fine-tune how colors appear, lower CRV means you’re basically stuck with one look.
Why CRV Isn’t a New CRI
Royer and his co-authors are clear: CRV doesn’t compete with CRI or TM-30. It complements them. Those older tools still score how good colors look for a single spectrum. CRV scores how much range you have to adjust that look, all while holding the white steady.
Think of it this way: CRI is a snapshot. CRV is the field of possible variations around that snapshot. And for tunable, multi-primary systems, that field can be wide—or surprisingly narrow.
Proof in the Numbers
To test CRV, the researchers built 132 theoretical multi-primary systems using real LED data. A simple four-primary system might manage a handful of unique metamers. A seven-primary system? It can generate billions of spectral combinations that hit the same white, with hundreds or thousands of visibly different color rendition options to choose from.
That’s the point: CRV reveals what tunable fixtures actually can do behind the scenes—and shows why adding more primaries can unlock more creative control.
A Quiet but Necessary Shift
So who needs CRV? Anyone who works with tunable lighting where color matters: museum conservators, retail merchandisers, workplace designers chasing both wellbeing and good looks. It won’t replace CRI or TM-30 on a spec sheet, but it might start showing up alongside it when clients want to know just how flexible their fancy new color tunable track light really is.
The paper, “A New Way to Understand the Color Rendition Performance of Multi-Primary LED Lighting Systems: Color Rendition Variability (CRV),” appears in LEUKOS, published June 11, 2025. The work was supported by the U.S. Department of Energy’s Lighting R&D Program.
For a lighting industry in the middle of a tunable revolution, it’s one more reminder that in this new era, even “white” light isn’t so simple anymore.
