CRI, TM-30-15... Wait, What?
So, what exactly is CRI? CRI stands for color rendering index—it’s a scale of measurement. It’s
a light source's ability to depict object colors "realistically" or "naturally" when compared to a
familiar reference source, such as incandescent light or daylight. When a manufacturer publishes
a CRI measurement, they communicate to their consumers how closely or accurately this lamp
compares to its incandescent or halogen counterparts, or even natural daylight.
CRI was established in 1965 and had a major revision in 1974. CRI is based on 8 color samples,
and uses a fidelity metric compared to a reference lamp. This type of measurement has worked well
for the last three decades, but due to the advancement of LED, CRI leaves out quite a bit of
information that can help a lighting designer make the best lamp choice. CRI is good, but it does not
tell the whole story.
TM-30-15 was established to measure what CRI leaves out. TM-30-15 uses 99 color samples
compared to CRI’s eight. Instead of using one metric, TM-30-15 uses four: Fidelity, Gamut,
Graphical, and Detailed. TM-30-15 uses a color vector graphic to show what colors the lamp
may bias. This feature is very helpful to a designer because it’s possible to have an 80 CRI lamp
with a greater red saturation show red objects better than a 95 CRI light source.
You may be asking yourself: “Why does it matter?”. A good analogy would be seeing everything
in tunnel vision. Sure, you can see what is ahead of you—but it doesn't give you the whole
picture. The one metric that is used for CRI just isn't enough to get a true understanding of the
lamp being measured. Currently, TM-30-15 is in the industry consensus phase and has not quite
yet become the standard. In time, manufacturers and specifiers will start to see the advantages
of using TM-30-15.
We’re only scratching the surface of the differences between TM-30-15 and CRI. To learn more,
visit http://energy.gov/sites/prod/files/2015/09/f26/tm30-intro-webinar_9-15- 15.pdf.