ADOPTED_FROM:EN ISO/CIE 11664-1:2019 This document 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 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.