The quality of light sources

This paper describes physical measures for quantifying the quality of light sources and their characteristics. Typical light sources, including incandescent lamps, fluorescent lamps and light emitting diodes, are first introduced and their performance is compared. The CIE colour specification system is then described, including physical quantities for specifying light sources such as colour temperature, spectral power distribution, luminance, illuminance, luminous efficacy, chromaticity coordinates, uniform colour spaces, a colour difference formula and a colour appearance model. Finally, the CIE colour rendering index, together with recent developments towards a new index, including CRI‐CAM02UCS, is described.