The CRI rating of light sources, is an old
out-of-date standard developed by the International Commission on
Illumination (CIE). It is a relative index which compares the relative
color reproduction ability of one light source to another for a
standardized FILM medium. 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.
This outdated light valuing method is mostly
irrelevant to digital photography because all digital cameras include
compensation for color temperature and are more accurate at 5500-6000K than
the 3200K color temperature of tungsten light. In reality tungsten light
does not render very well as it has an abundance of red and infrared (heat)
and is relatively weak in the blue part of the spectrum. In reality, light
sources that are closer to 5500K (like the ALZO Cool Lites) will render
color better in a digital camera than tungsten light.
Conclusion: We include CRI ratings in our
product descriptions because many customers request it as it is the only
reference commonly used. But in terms of using CRI to determine the
rendering ability of a light source CRI is useless. In reality we are
anxiously waiting for the CIE to develop a better index that address the
many light generation technologies present today that are far better than
tungsten sources.
