Historical development of CIE recommended color difference equations

In 1976 the CIE recommended two colour difference formulae, the CIELAB and CIELUV formulae, to promote uniformity of practice pending the development of a better formula. While some of the arguments in favour of the recommendation were political, there were also sound technical reasons for choosing the two formulae. The discussions leading to the recommendation and the reasons that led the CIE to its decision are reviewed. In particular the reasons for the modification of the 1964 (U*, V*, W*) formula to arrive at the CIELUV formula are given, and the derivation of the constants (116, 16, 500 and 200) in the CIELAB formula is explained. Most of the data presented are taken from CIE Committee minutes and correspondence.