Effect of unequal stimulus size on color matching performance

Color matching functions (CMFs) play important roles in color specification, characterization, and reproduction. Though the CIE 1931 2° CMFs are widely used in practice, its well-known weaknesses and poor performance have motivated great efforts in this field. Most studies, however, mainly focused on the performance of CMFs in characterizing stimuli with different spectral compositions or color differences perceived by individual users. In this study, we specifically focused on how the stimulus size, in terms of the field of view (FOV), between 2° and 10° affected the color matching performance, especially when the two stimuli differed in sizes. The results suggested that the color matching results of the 2° FOV were significantly different from those of the other four FOVs (i.e., 4°, 6°, 8°, and 10°). The CIE 1931 2° and 1964 10° CMFs had poor performance in characterizing the color matches, which did not support the recommendation made by the CIE for using the 10° CMFs for stimuli beyond 4°. Also, the CIE 2006 framework for deriving the cone fundamentals for different FOVs seemed to have a good performance for stimuli, except the blue stimulus, with an FOV between 4° and 10°, as evaluated in an (x,y)-like cone fundamental diagram.