This CIE Standard replaces ISO/CIE 10527:1991. This Standard contains only minor
changes from the previous Standard, it has now been clarified that the values of the
colour matching functions apply for standard air to make the Standard conform to
other CIE photometric and colorimetric data.
Colours with different spectral compositions can look alike. An important
function of colorimetry is to determine whether a pair of such metameric colours will
look alike. It has long been the practice in colorimetry to make use of sets of colourmatching
functions to calculate tristimulus values for colours: equality of tristimulus
values for a pair of colours indicates that the colour appearances of the two colours
match, when they are viewed in the same conditions by an observer for whom the
colour-matching functions apply. The use of standard sets of colour-matching
functions makes the comparison of tristimulus values obtained at different times and
locations possible.
This International Standard specifies colour-matching functions for use in
colorimetry. Two sets of colour-matching functions are specified:
Colour-matching functions for the CIE 1931 standard colorimetric observer
This set of colour-matching functions is representative of the colour-matching
properties of observers with normal colour vision for visual field sizes of angular
subtense from about 1° to about 4°, for vision at photopic levels of adaptation.
Colour-matching functions for the CIE 1964 supplementary standard colorimetric
observer.
This set of colour-matching functions is representative of the colour-matching
properties of observers with normal colour vision for visual field sizes of angular
subtense greater than about 4°, for vision at sufficiently high photopic levels
and with spectral power distributions such that no participation of the rod
receptors of the retina is to be expected. The values in the tables of the colour matching functions and chromaticity coordinates of the CIE 1931 and 1964 standard colorimetric observers are identical
with those in the previous standard.
