Scaling procedures for specifying color appearance

Abstract

AbstractColors of objects are often specified by color matches in some standard colorimetric system. While color‐matching allows a color to be reproduced accurately, it does not specify what the color actually looks like. Color appearance (i.e., hue, saturation, brightness) can be measured by direct psychophysical scaling techniques; however, these methods have not been standardized and have been confined mostly to the laboratory. We have examined several variants of continuous, numerical scaling of hue and saturation to find a procedure that is usable, even by untrained observers. Appearances of monochromatic, equal‐luminance light flashes were scaled along the dimensions of the unique hue sensations (red, yellow, green, blue) and apparent saturation. These functions were obtained for various stimulus conditions, including changes in stimulus luminance, size, and eccentricity. Multidimensional scaling methods were used to derive metrically uniform color appearance diagrams from the hue and saturation scaling data. Validity of the scaling procedures was assessed by deriving well‐known visual functions, such as wavelength discrimination, from the color appearance diagrams. The direct scaling method was shown to be generally useful, and both trained and untrained observers readily and reliably used the technique.