CIE 1931 standard colorimetric system [X, Y, Z]
system for determining the tristimulus values of any spectral power distribution using the set of reference colour stimuli [X], [Y], [Z] and the 3 CIE colour-matching functions adopted by the CIE in 1931NOTE 1 is identical to V(λ) and hence the tristimulus values Y are proportional to values of luminance.NOTE 2 This standard colorimetric system is applicable to centrally-viewed fields of angular subtense between about 1° and about 4° (0,017 rad and 0,07 rad). NOTE 3 The CIE 1931 standard colorimetric system can be derived from the CIE 1931 RGB colorimetric system using a transformation based on a set of 3 linear equations. The CIE 1931 RGB system is based on 3 real monochromatic reference stimuli. See also CIE 15 Colorimetry