scope:

This part of 105 provides a colorimetric method for calculating an estimate of the magnitude (and
optionally the direction) of the change in the perceived colour of a textile specimen when the chromaticity of the illumination by which it is viewed is changed. It therefore provides an estimate of the colour inconstancy of the specimen.
NOTE 1: Colour inconstancy and metamerism are related but distinct. With respect to a change in the quality of illumination,
a) colour inconstancy is the extent of change in the colour appearance of a single specimen,
b) metamerism is the extent of change in the colour difference between two specimens.
This part of 105 therefore provides a method for assessing (a) but not (b).
NOTE 2: Comparison of the results of this method and those from visual assessments is valid only when the visual assessments are made
a) in lighting of the same spectral power distributions as used in the colorimetric calculations,
b) with the specimens illuminated at 1 000 lux to 4 000 lux,
c) by an assessor who is fully adapted to the relevant viewing conditions.