明暗スケール作成の試み
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概要
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Several different scalings of gray series of surface color have been attempted thus far but none of them are satisfactory from the point of view of psychological uniformness. Meanwhile the problem is becoming increasingly important in the field of the applied visual sciences connected to TV engineering, and others. The Lagorio gray scale was spaced rather <I>a priori</I> on logarithmic steps of reflectance implicitly assuming Fechner's law, but its psychological uniformness has not necessarily been assured We checked the psychological distances of grayness over Lagorio scale in terms of the discrimination limen of grayness and constructed a new scale from the obtained threshold values.<BR>In the first part of the experiment, the averages of discrimination limens of grayness at five different points on the Taguchi's modified Lagorio gray scale were determined with 30 adult subjects. The conditions of illumination of the gray samples were about 1000 lx in the day light and about 50 lx under electric light. Backgrounds were of three kinds, i.e., white, gray and black.<BR>As the results, we obtained the formula<BR>ΔR/R=(-.0903) log R+.2429<BR>for the condition of daylight and white background, where R is the relative reflectance of the grayness. For other experimental conditions. the linear prelations as above held good but with different coefficients. Relative discrimination limens at 33 different values of R were computed from this formula and a new gray scale with supposedly equal sense distance was constructed therefrom.<BR>In the second part of the experiment, several gray samples were specially prepared from the new scale and the discrimination limens at several points were checked. The limens expressed in terms of scale values were found to be equal to the gray series and the uniformity was confirmed.<BR>It was concluded that the differential limens in Lagorio scale values were not uniform in such a way that the higher the reflectance is, the smaller is the limens, and likewise, the lower the former, the greater the latter. The new gray scale is offered as much more adequate than Lagorio scale.
- 公益社団法人 日本心理学会の論文