Yasuki YAMAUCHI^* and Keiji UCHIKAWA

Department of Information Processing, Tokyo Institute of Technology, 4259-G2-1 Nagatsuta, Midori-ku, Yokohama 226-8502, Japan

(Received March 2, 2004; Accepted April 27, 2004)

A series of experiments were conducted to find the effects of non-uniform illumination on the surface-color mode perception. Two patterns of the illumination, one-sided illumination and a spotlight, were simulated. Observers adjusted the luminance of the test stimulus so that it just started to appear partially as an aperture-color mode. We found that the upper-limit luminance was significantly lower for all test colors when the directions of the gradient between the test stimulus and the surrounds did not match. On the other hand, in the spotlight conditions the upper-limit luminances changed only when it was contained in the spotlighted area. Our results suggest that the brightest stimulus in the scene does not work as a cue, and that the visual system takes the influence of illumination into account in order to set a criterion for the judgment for the color appearance of the mode.

Key words: Mode of color appearance, surface-color mode, luminance gradient, non-uniform illumination, color vision

^*Present affiliation: Technology & Development, Development & Manufacturing Group, Fuji Xerox, Co., Ltd. Email address: yamauchi@u.ip.titech.ac.jp