Chromatic Response Curves of Surface Colours

Abstract

Basic data in colour vision such as chromatic response curves were obtained with aperture colours. It is not possible to apply the cancellation technique to define redness or yellowness components etc in a surface colour. A method was developed to obtain such information (Indow, 1987 Die Farbe34 253 – 260), which was based on the expanded form of multidimensional scaling. The results by an improved method are presented. First, it is shown how multiattribute perceptual differences between two Munsell colours, P j, P k, are predicted by distances ^ djk in the current Munsell solid. Colour differences djk are defined by matching with lightness differences in Munsell gray scale and root-mean-squares of ( djk - ^ djk) is 0.2∼0.3 in the unit of Munsell Chroma C. Second, principal hue vectors falpha, alpha= R, Y, G, B, or P in addition, are defined in the current Munsell solid. As shown before, fB is shifted from 5 R in the direction of 5 P, irrespective of whether P is included or not. Overall root-mean-squares of (scaled values of principal hue a in a colour j-coordinates of P j on falpha) is about 0.6 in the unit of C. On the basis of these findings, it becomes possible to define principal hue components for any Munsell colours and hence chromatic response curves are obtained as a function of H, V, and C.