Colorimetric evaluation of daylight simulator sources

Abstract

AbstractThe color shift of a sample due to a change in illuminant can be expressed either in terms of the CIE General Color Rendering Index, Ra, based on the average for eight color samples, or in terms of the CIE Metamerism Index MIvis, the average for five pairs (or couples) of samples. It is shown that, in an ideal case where the eight samples constitute four complementary pairs, the value of the average for eight can be predicted accurately from the average for only four of the eight samples. This is approximately also the case for a prediction based on four of the actual eight CIE samples, but in this case there is some uncertainty in the predicted Ra values. For MIvis, a useful approximation in value can be obtained using only two of the five defined couples. Finally, it is shown that Ra and MIvis evaluate illuminants in largely the same way.