Pontawee PUNGRASSAMEE¹, Mitsuo IKEDA^1,2, and Aran HANSUEBSAI¹

¹Department of Imaging and Printing Technology, Chulalongkorn University, Bangkok 10330, Thailand
²Department of Photonics, Ritsumeikan University, Nojihigashi, Kusatsu, Shiga 525-8577, Japan

(Received July 3, 2006; Accepted February 22, 2007)

The theory of the recognized visual space of illumination (RVSI) is that the color appearance of objects in a space is determined in relation to its recognition axis RX whose direction is determined by the brain action to adapt to the illumination in the space. Thus the color constancy holds. RX is applicable to objects in the space but not to an object or a portion that does not belong in the space in terms of illumination, that is to say, the luminance of which is too high based on the illumination for that space. In that case the color appearance would be determined in relation to the fundamental axis FX and the color constancy would not hold. In the present paper the chromaticity points were measured for a test patch that appeared achromatic for various luminance of the patch. The points were close to the color of illumination to indicate the color constancy when the luminance was low enough to assure its appearance as the object color, but they departed from the color of illumination and approached the colorimetrically achromatic color. The color constancy gradually failed for the test patch with the high luminance when the color mode became an unnatural object color and then a light color.

Key words: color constancy, color appearance, color appearance mode, illumination, recognized visual space of illumination, achromatic perception