Abstract
We defined the actual contrast of a visual target at a fovea as an EFFECTIVE CONTRAST in our previous paper. This is not the same as the nominal contrast of it, because the stray light in the eyeball is superimposed on the foveal image. This concept leads to simplify the treatment of visual ability, because the effects of size of targets are eliminated and the visual ability can be determined only with contrast sensitivity. We have already confirmed the availability and applicability of this concept in the case of the unidirectional targets. In this paper, the applicability of above concept to the rectangular figures is discussed based on the results of visual experiments, as the first step to extend its application to the general visual objects. The results obtained may be summarized as follows : 1) The EFFECTIVE LUMINANCE, which is defined as a foveal luminous stimulus taking account of the stray light in the eyeball, is more useful concept than the effective contrast to deal with the visual problems systematically. 2) For the rectangular figures, above concept is also applicable and available to estimate the visual ability. 3) Some examples of the calculations of the effective luminance ratios for the figures composed of rectangular elements are also presented. Further visual experimental studies are necessary to apply this concept to detail recognition of the visual objects.
