Color Rendering Index

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Understanding CRI (Color Rendering Index)

Color Rendering Index (CRI) is a measure of how good a light is at showing an objects "true" color. The CRI does not measure the color of the light itself, (that is measured by degrees Kelvin) but the color of items being revealed by that light source. The Index measures from 0 to 100. A perfect 100 is how an object looks in unfiltered sunlight. When lighting with an artificial light source, the closer that light source gets to portraying the same colors as revealed by the sun, the closer it gets to 100. An incandescent fixture is supposed to be 100 on that scale while. Fluorescent fixtures can range anywhere from 50-98 CRI. LED lights usually have about 80 or better CRI, with many manufacturers claiming CRI of up to 98. 

Light sources with a CRI of 80 to 90 are usually regarded as "good" and a CRI of 90+ is considered excellent, because the higher the CRI, the better the color rendering capacity.  However, a CRI approaching 100 is not necessarily what you should be looking for. The space you want to light might look better with 85 CRI than with 100. It is all a matter of opinion. Generally any light with a CRI of 85 looks good, and does not distort colors to feel unnatural. Old style LED bulbs were known to give off a blue or grey light that looked unfamiliar and cold. Those bulbs would probably land in the 60-80 CRI range.

CRI is different than  color temperature. Color temperature is measures in degrees Kelvin. To give an example, a 4000K LED lamp could have a CRI of 70, but another 4000K LED lamp can have a CRI of 90.

Typical requirements for light CRI:

Photograpy and video over 90

residential over 85

Commercial office over 80

Industrial buildings 70