This is an attempt to determine the primaries corresponding to the fundamental sensations of the Young-Helmholtz theory. Unlike previous attempts by various authors, this determination is based solely on color-mixture data pertaining to the trichromatic observer. It is shown that the primaries can be derived from the color-mixture data of the average trichromate with reasonably small uncertainty, if only the one hypothesis is made that each of the three response functions has a certain simple geometrical character, resembling the standard luminosity function. This hypothesis is suggested by the purely physico-chemical character of the retinal processes. An analysis of the situation shows that in order to explain the behavior of color blind observers by the response functions thus obtained it is necessary to assume that “inner” dichromatism—such as deuteranopia—consists not in the absence of one of the fundamental responses, but in the failure of the mental organ to distinguish qualitatively between two of the fundamental responses. A satisfactory quantitative account is given of all the known forms of dichromatism.
A colorimetric system based on the “natural” or Young primaries compares favorably with the conventional I.C.I. system.
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