Color rendering is an evaluation of how colors appear under a given light
source. For example, a shade of red can be rendered pinker, yellower, lighter or darker dependent on the
characteristics of the illumination falling on it. Color rendering must be considered
a subjective evaluation because it depends to some degree on the coloration
that is desired.
Efforts to quantify the color rendering ability of a light source have achieved limited success. However, one system being used today for describing color rendition was developed by the CIE (Commission Internationale De l'Eclairage) the International Lighting Standards Commission. The system is referred to as the Color Rendering Index or CRI. This method uses eight test colors and expresses the relative ability of the light source to render those eight colors as a standard reference illuminant would render those colors. The CIE method has limitations, but it does afford a means of comparison if the light source and the reference source have the same color temperature.
Incandescent references are used for lamps having a color temperature of 5000°K and below, while various phases of daylight are used for lamps of higher color temperatures.
