A series of experiments were carried out to study effects of a partial change in luminance on the limit of the surface-color mode perception. A CRT monitor displayed the stimuli that contained an area whose luminance was changed incrementally or decrementally. We tested several spatial positions and luminance change ratios of the area for two configurations of the stimuli. Observer adjusted luminance of the test color so that it just ceased to appear as an attribute of the surface. Our results indicated that the upper-limit luminance of test stimulus tend to change only when the test stimulus was located inside the brighter/darker area. The same results were obtained with the stimulus whose configuration gave an impression that the test stimulus appeared to belong to the same group as the stimuli whose luminance was changed. It is suggested that the perceptual organization of the stimuli, not an apparent brightest stimulus, mainly works as a cue for the judgment of color appearance mode.

It is a common understanding that white serves as an “anchor” for the visual system for lightness scaling purposes. By lightness we are referring to surface color perception in the achromatic domain. The importance of “surface white” is stated also in the literature about luminosity perception, where it is often claimed that in order for a region of the visual field to appear as self-luminous, its luminance must be somewhat higher than the luminance of a surface perceived as white under the same conditions of illumination. Implicit in this assumption is that the visual system is able to determine what is to be seen as white instead of luminous, glowing or light gray. A “highest luminance rule”, eventually corrected by an area factor, seems so far to be the best candidate. This approach has been applied to several lines of data with apparent success. However, below we will describe two experiments, one concerning lightness and the other perceived luminosity, that show the severe limitations of the highest luminance rule hypothesis.