Uniformities in OSA-UCS and in NCS tested by color difference prediction based on principal hue components

摘要

The OSA uniform color system is a 3-D collection of color samples according to the regular rhombohedral structure in which each color is surrounded by its 12 nearest neighbors, all perceptually equally different (local uniformity). The Swedish NCS system is a 3-D collection of color samples that vary gradually in each of the three perceptual attributes. It is not clear that this arrangement implies all neighboring pairs along the respective coordinates being perceptually equally different (local uniformity). Of pairs (j, k) of interest, predicted color differences d_(jk) were calculated that have the following property. Suppose an observer selects a pair of Munsell grays (Va, Vb) that matches in size with the color difference between (j, k), then d_(jk) = | Va-Vb | is predicted by d_(jk) , on the average, with error of 0.34 in Munsell V-unit. Variation of d_(jk) in this unit was in the order of 0.22V for nearest neighboring pairs (j, k) in various cleavage planes of OSA-UCS and in the order of 0.11V for neighboring pairs (j, k) along s-coordinate and c-coordinate in sheets with fixed hue of NCS. Both were well within the prediction error range, but some systematic trends in values of d_(jk) were found.