Color-rendering index
Overview
Color
Color or colour is the visual perceptual property corresponding in humans to the categories called red, green, blue and others. Color derives from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors...
s of various objects faithfully in comparison with an ideal or natural light source. Light sources with a high CRI are desirable in color-critical applications such as photography
Photography
Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...
and cinematography
Cinematography
Cinematography is the making of lighting and camera choices when recording photographic images for cinema. It is closely related to the art of still photography...
. It is defined by the International Commission on Illumination
International Commission on Illumination
The International Commission on Illumination is the international authority on light, illumination, color, and color spaces...
as follows:
Color rendering: Effect of an illuminant on the color appearance of objects by conscious or subconscious comparison with their color appearance under a reference illuminant
The CRI of a light source does not indicate the apparent color of the light source; that information is under the rubric of the correlated color temperature (CCT).
CRI's ability to predict color appearance has been criticized in favor of measures based on color appearance models, such as CIECAM02
CIECAM02
Published in 2002 by the CIE Technical Committee 8-01 , as of 2008 CIECAM02 is the most recent color appearance model ratified by the CIE, and the successor of CIECAM97s.| quote=The CIECAM97s model was adopted by the CIE in 1997 for color imaging applications. It includes forward and reverse modes...
and, for daylight
Daylight
Daylight or the light of day is the combination of all direct and indirect sunlight outdoors during the daytime. This includes direct sunlight, diffuse sky radiation, and both of these reflected from the Earth and terrestrial objects. Sunlight scattered or reflected from objects in outer space is...
simulators, the CIE Metamerism Index.
CRI is not a good indicator for use in visual assessment, especially for sources below 5000 Kelvin
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
(K).
A newer version of the CRI, R96a, has been developed, but it has not replaced the better-known Ra general color rendering index.
Researchers use daylight as the benchmark to which to compare color rendering of electric lights.
