輝度変化に伴うlightness及びbrightnessの知覚

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  • キド ヘンカ ニ トモナウ lightness オヨビ brightness ノ チカク
  • Perception of Lightness and Brightness with Changing Luminance

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The possibilities of the application of AL theory by H. Helson (1964) to the problem of lightness constancy have been argued by the present author (1970). As far as his quantitative equation is concerned, Helson fails to take account of the factor of the illumination level. Further studies on the relationships between adaptation reflectance and the level of illumination should be required. Moreover, in spite of the fact that lightness or achromatic color in surface mode could appear with brightness impression, little attention has been paid to the phenomenal relation between lightness and brightness. The present experiments were designed to examine the following problems: (1) how change of illumination affects the adaptation reflectance (AL), and (2) the relationships between lightness and brightness responses under the condition that achromatic "surface color" appears. The subjects were required to make categorical judgments for both lightness and brightness of the series stimuli, 6 achromatic color squares, on black, medium gray and white backgrounds under various illumination levels. The following findings were obtained. First, the shifts of adaptation reflectance with changing illumination and their dependence upon the background reflectance were observed. Second, it was proved that the functions of lightness judgments and of brightness judgments were different, and the relation between them depended on the reflectance of the background: that is, on black background the judgments of brightness of series stimuli correlated with the judgments of lightness, while on white background there was no correlation between the judgments of lightness and of brightness. Based on these results, the role of the background reflectance as a factor determining the relationships between lightness and brightness responses was discussed, and it was argued that highest luminance area might be functioning in much the same way for judgments of brightness and for judgments of illumination.

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