写真像の鮮鋭度

II: 鮮鋭度とレスポンス関数の関係

抄録

In the provious paper (Part 1), a study on the relation of sharpness to the characteristic curve of photographic materials was reported. This paper presents the relation between psychological sharpness and sine wave response function of optical transfer system and gives the practical evaluation of sharpness.
A simple exposing apparatus has been constructed, and various pictures (portrait, edge, texture, and sight) with different sharpness have been taken.
Eight sorts of evaluation fanction derived from sine wave response function of image R(u, v), response function of the eye r(u, v), and contrast of image C are given. The numerical values of evaluation functions of those pictures are calculated and compared with psychological sharpness of respective pictures. The relations between evaluation functions and sharpness are shown in figures.
The results of this study indicate that, among these evaluation functions, the function S₄=∫∫_??_{R(u, v)·r(u, v)}²dudv agees best with the psychological sharpness.