In chromaticity contrast experiments complementary colors were applied. When the surrounding field was blue, fluorescent illumination (FL) strengthened contrast induced on a surrounded yellow field. A red surrounding field yielded strongest contrast effect under incandescent light (IL). The perimetric thresholds of all colors were increased when changing from IL to FL, i.e., they could be recognized further out in the periphery. The rise was strongest for blue.

Recently developed types of indirect psychophysical scaling method served as starting point in finding a handy procedure for measuring differences in the degrees of ‘color constancy’. A design for carrying out categorical comparisons with color paper proofs was constructed. The raw scores, given as percentage distributions, prove transformable into standard scale values. These demonstrate the shifted positions of the colors in question when presented in alternating conditions of illumination.

Some completion is given on a method for measuring color constancy criticized by Pietarinen (1966). Pietarinen's assumption, that our rating categories did not represent a single rank order, is untenable. A closer examination of the stimuli of the original study shows that the color sets included in, e.g., the Ostwald system allow at least for ordinal ranking of the responses, which was the main purpose of our investigation.