Kitirochna RATTANAKASAMSUK and Hiroyuki SHINODA

Human Vision Laboratory, Graduate School of Science and Engineering, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan

(Received November 7, 2005; Accepted July 27, 2006)

Perceptual achromatic setting has been claimed to be a method of assessing the recognition of illumination in an environment. The result, however, is not spatially valid because of some effect of an immediate area of the test (local effect). We considered a method for excluding this local effect from the assessment. We hypothesized base on the co-planar theory and the recognized visual space of illumination theory that a depth separation between the test and its immediate area would be an effective way. In the first experiment, the perceptual achromatic setting was conducted in a natural scene, with several test luminance levels. The perceptual achromatic locus from two conditions was compared. One condition is the test pasted on a chromatic surround. The other is the test fronto-parallelly separated from the surround. In the second experiment, the perceptual achromatic setting was conducted at the several depth separations. We found that the depth separation decreases the local effect but it was not completely excluded.

Key words: recognition of the illumination, local effect, chromatic induction, depth separation, depth perception