The color rendering index (CRI) is a quantitative measure of the ability of a light source to reveal the colors 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 neonatal care, photography and cinematography.

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). The CRI is determined by the light source's spectrum. The value often quoted as 'CRI' on commercially available lighting products is properly called the CIE Ravalue, 'CRI' being a general term and CIE Ra being the international standard color rendering index.

Numerically, the highest possible CIE Ra value is 100, and would only be given to a source identical to standardized daylight or a black body (incandescent lamps are effectively black bodies), dropping to negative values for some light sources. Low-pressure sodium lighting has negative CRI; fluorescent lights range from about 50 for the basic types, up to about 90 for the best tri-phosphor type. Typical LEDs have about 80+ CRI, Our high CRI LED lights have over 95 CRI.