Abstract

Luminance, which is measured by the heterochromatic flicker photometry with high-temporal frequency stimuli, is often referred as the intensity dimension of the achromatic form pathway. This is supported by the fact that sharpness of the edges is minimized at isoluminance as has been suggested by minimally distinctness border (MDB) experiments. On the other hand, brightness measured by direct brightness matchings is another intensity dimension for an achromatic process. It may be that brightness is the achromatic dimension for low-spatial and low-temporal frequency domain while luminance is that for high-spatial and high-temporal frequency domain. However, there are two reports that suggest that luminance controls achromatic form perception in relatively lower spatial and temporal frequency stimuli; i.e. the strength of blurred edges 1), subjective contours2) and shadows2) is minimized at isoluminance. We used shading figure in two colors (Fig. 1) whose spatial frequency was controlled by the slope of the gradual luminance change. The iso-achromatic point could be measured by the relative luminance at which the impression of shading was minimized or disappeared completely.

© 1992 Optical Society of America