correlated colour temperature

CCT

T_cp

temperature of a Planckian radiator having the chromaticity nearest the chromaticity associated with the given spectral distribution on a modified 1976 UCS diagram where u′, are the coordinates of the Planckian locus and the test stimulus

Note 1 to entry: The concept of correlated colour temperature should not be used if the chromaticity of the test source differs more than from the Planckian radiator, where , refer to the test source, and , to the Planckian radiator.

Note 2 to entry: Correlated colour temperature can be calculated by a simple minimum search computer program that searches for that Planckian temperature that provides the smallest chromaticity difference between the test chromaticity and the Planckian locus, or for example by a method recommended by Robertson, A.R. "Computation of correlated color temperature and distribution temperature", J. Opt. Soc. Am. 58, 1528-1535, 1968. (Note that the values in some of the tables in this reference are not up to date.)

Note 3 to entry: The chromaticity diagram originally used to determine the correlated colour temperature was the CIE 1960 uniform-chromaticity-scale diagram. The CIE 1976 uniform-chromaticity-scale diagram is a modified version of the CIE 1960 uniform-chromaticity-scale diagram and is equivalent to the (u, 3/2 v) diagram.

Note 4 to entry: The correlated colour temperature is expressed in kelvin (K).

Note 5 to entry: This entry was numbered 845-03-50 in IEC 60050-845:1987.

Note 6 to entry: This entry was numbered 17-258 and 17-130 in CIE S 017:2011.