The CIE (Commission Internationale de l’Eclairage) is the international standards organization responsible for setting standards for color and color measurement.
CIE 1976 U.C.S Chromaticity Diagram.
U.C.S stands for Uniform Color Space, Uniform Color Scale, Uniform Chromaticity Scale, or Uniform Chromaticity Space. The chromaticity diagram is a tool to specify how the human eye will experience light with a given spectrum.
The CIE U.C.S is another name for the (u, v) chromaticity space devised by David McAdam.
In 1976 the CIE recommended the adoption of two new color spaces (CIELUV and CIELAB). CIELUV is only a minor modification of the CIE 1964 color space, and includes a new u’v’ chromaticity diagram which replaces the 1960 UV diagram. Correlated color temperature can be calculated using the new diagram, leading to somewhat different results.