Abstract
In the previous papers, we defined 'effective luminance' as a luminance of a retinal image at a fovea after intraocular scatter, and found that the difference in visual ability caused by the size of a visual target depends only on the difference in its effective luminance for the detection of a simple shaped target. In this paper, we show the systematical method to calculate the effective luminance at any visual point for an arbitrary shaped visual target. The calculation is approximately performed with dividing the target into small regular squares, and the psychophysical measurements using circular visual targets confirm that the calculated value has a practically sufficient accuracy. From the comparison of the estimated visual thresholds of landolt rings based on the effective luminance with the visual experimental data of Nakane and Itoh, from which a standard equivisual acuity curves are deduced, it is found that the concept of the effective luminance is available for a recognition of an arbitrary shaped figures as well as the detection of rectangular figures presented in the previous paper. And examples of the equivisual acuity curves for a few types of visual targets are also presented. By introducing the effective luminance, the visual ability can be determined only with the luminance difference threshold for any visual object. Above results suggest that 'effective luminace' is a very useful concept for the study on the visual problems.
