Yuwadee THIANGTHANGTUM, Mitsuo IKEDA and Hiroyuki SHINODA

Department of Photonics, Faculty of Science and Engineering, Ritsumeikan University, 1-1-1, Noji-higashi, Kusatsu-shi, Shiga-ken 525-8577, Japan

(Received March 25, 2004; Accepted November 15, 2004)

The border luminance of the test stimulus between the natural and unnatural object color, _nB_u was obtained for different spatial sizes of the immediate surround to prove that _nB_u can be determined based on a new recognized visual space of illumination (RVSI) that is assumed to be constructed for the immediate surround separately from the RVSI for the subject's room itself. The _nB_u of five test stimuli were determined for six different sizes covering from zero to 1866 cm² with four different lightnesses, N4, N6 and N8, while keeping the room illuminance constant at 100 or 600 lx. The results showed that luminance of the border _nB_u gradually decreased as the size of the immediate surround was increased and that the decrease was larger for immediate surround with lower lightness. The results were interpreted as showing a new RVSI constructed for the spatial extent of the immediate surround of the test stimulus, and the RVSI was more completely constructed for larger spatial size of the immediate surround.

Key words: color appearance mode, object color, light source color, recognized visual space of illumination (RVSI), room illuminance, border luminance, surround size, size effect