The CRI (Color
Rendering Index) rating of light sources, is an old standard developed by the
International Commission on Illumination (CIE) in the 50's. It is a relative
index which compares the relative color reproduction ability of one light
source to another. The maximum value of 100 is given to Tungsten light
sources, therefore all other light sources including sunlight will have
values less than 100. This was an important reference for film
photography because tungsten balanced film rendered perfectly in
tungsten light and color shifted for almost all other light sources that have
lower CRI values.
The CRI light
valuing method is mostly irrelevant to video cameras because of "white
balance" compensation for color temperature. In reality tungsten light has an
abundance of red and infrared (heat) and is relatively weak in the blue part
of the spectrum.
Conclusion: CRI has very little value in determining the
color rendering ability of a light source in video production. Most
daylight balances light sources with color temperature of between 5000 to
6000 K will render color better than Incandescent. Daylight HID (HMI)
provides the best color rendering when mixed with daylight. Daylight
Fluorescent is our second choice but may require the addition of 1/2 minus
green filtering. LED lighting is difficult to judge at this time as
color temperature varied from one manufacturer to another.
