Abstract
We usually have good color constancy in natural environments where we can easily recognize the structure of a space and illumination. In our previous study, we have demonstrated the effects of a natural and an unnatural viewing condition on color constancy. (Mizokami & Yaguchi, 2007 ECVP). Observers judged a color of a test patch placed either in a front or a back room. Two rooms were connected by a window and illuminated by reddish and white lights, respectively. The immediate surround of the patch was always the white wall of the back room under white illumination. Results showed a loss of color constancy under the unnatural viewing condition where the spatial structure was distorted by a kaleidoscope-type viewing box, suggesting the importance of naturalness and spatial factors. We also found a strong contrast effect by the immediate surround, but it was not clear if it was due to a local contrast or the ‘white’ illumination of the back room became a strong anchor. In this study, we examined how color constancy and color contrast were changed by a variety of immediate surround conditions under the natural and unnatural viewing conditions to find factors affecting the appearance of a test patch. We tested the combinations of white, reddish, and green illuminations as well as different background colors. The results showed stronger local contrast effects on the color judgments of the test patches under the unnatural viewing condition than the natural viewing condition in all combinations of illumination color. They suggest that color appearance is not determined by merely a local contrast but the color of illumination under a natural viewing condition, whereas it strongly relies on the immediate surround in the case of an unnatural condition that we are not able to obtain the accurate recognition of a space and illumination.
Supported by JSPS Grant-in-Aid for Young Scientists (Start-up).