Spectral saturation and its relation to color-vision defects.

Abstract

Saturation thresholds were measured at 19 spectral points by finding the proportion of hue which had to be added to white of 5000[degree]K. to make the mixture appear just discriminably colored. Eight subjects, 2 normal and 6 with varying degrees of color vision defect, showed that spectral saturation for the color blind observers was generally lower than for the normal observers. The extent of this difference was related to the degree of color defect; the curves for the true dichromats deviated most from the normal values, while those for the color blind lay between the two. A shift in the relative saturation of various spectral hues was related to the degree of color defect. The greatest change in saturation occurred in the blue-green region of the spectrum and the least in the yellow and yellow-green regions. Blue-green for the normal observer was a highly saturated hue, for the color blind it was less saturated, and for the dichromat it was completely desaturated, i.e., it matched white. The practical value of these findings is that they may provide a basis for the construction of a quantitative scale of color blindness.