Color-rendering capacity of illumination.

A new measure called color-rendering capacity is developed, by applying some of the concepts used in communication engineering, to describe another aspect of the color-rendering properties of illumination, i.e., the maximum possible number of different colors that can be displayed by a given illumination. It is a relative measure expressed as a dimensionless parameter between zero and unity, depending only on the spectral power distribution of the illumination. The computer program involved in calculating this parameter and calculated examples for several different light-source types are presented. By reference to this parameter, the prediction for four different fluorescent lamps about the extent to which a lamp can make an average chromatic environment appear colorful and bright is in general agreement with the existing observation. Another potential use of this parameter, in collaboration with the luminous efficacy, as a relevant indicator of the visual efficiency of illumination is also discussed.