Colour Perception and Colour-Rendering:

Experiments with coloured shadows, contrasts effects, double and triple projections, and chromatic illuminants all show that colour perceptions, in terms of hue, saturation, and brightness, are not direct functions of the physical properties of the stimulus nor yet of the psycho-physical properties (chromaticity and luminance), but depend on the relation of each colour patch to the totality of the visual scene— a relationship expressed by polarity and compensation. The mental process of fitting concept to percept in making sense of the sensations is also important.It is suggested that in spite of the subjective nature of colour perceptions, the colour-rendering properties of an illuminant could well be determined by the perceived colours of objects, taking into account chromatic adaptation, and using the degree of colour constancy as a measure of success. Reciprocal chromaticity, specifying object colours as selective darkenings of the illuminant, might be found appropriate to this method.