Colour rendering capacity and luminous efficiency of a spectrum

The colour rendering properties of illumination may be considered to fall into two basic types. Type A includes those in which a comparison between a resultant colour and a reference colour is involved, and it matters whether the resulting colour can match the reference one( 1, 21; type .~ includes those in which no such comparison is involved and it does not matter whether the resulting colour can match some particular colour 13--7) . A wellknown measure for type A properties is the CIE colour rendering index, which measures the degree to which the perceived colours of objects illuminated by the source conform to those of the same objects illuminated by a reference illuminant. This Note discusses a measure for type B properties, the colour rendering capacity (CRC), which measures a spectrum’s potential for revealing a large number of different colours. From a visual communication perspective, light with a high CRC is more effective as a carrier of visual information. The following sections address the derivation, implication and calculation of CRCS.