周辺視野明度と色の純度差弁別について

抄録

The discrimination of purity of color stimulus was investigated in terms of the standard deviation of color matching on the purity dimensions for 473, 490, 540, 573, 612 and 542c in the dominant wave-length (mμ) on CIE (x, y) chromaticity diagram. The apparatus was essentially a type of color paper mixer; the results of the experiment thereby being limited to apply only to a part of color gamut reproducible by the mixing of surface colors of matte paper. The data were collected by 100 matchings by 5 observers, 20 matchings by each, for a stimulus color.
The brightness of surrounding field was varied in three ways; darker (condition A), equal (condition B) and brighter (condition C) as compared with the stimulus. The stimulus brightness being constant, the phenomenal brightness of the stimulus was changed therefore by contrast effect from dark (in the condition C) to bright (in the condition A).
It was found that high phenomenal brightness value generally improved the color matching accuracy but its characteristics was different from one half domain of the wave-length to another half. For the color stimuli of the dominant wave-length of 490-540-573mμ, the accuracy was more improved from the condition B to A than from C to B. On the other hand, for the stimuli of the dominant wave-length of 612-542c-473mμ, it was improved from C to B but not at all from B to A (Fig. 2 & Fig. 3).
A psychological scale of chromatic saturation was formulated taking the standard deviation of color matchings as the unit. Every two chroma steps in Munsell chroma scale approximately corresponded with every ten units of standard deviation for the color stimuli of 612mμ and 473mμ in dominant wave-length. This was also partly true for 542cmμ. For the color of 490, 540 and 573mμ in dominant wave-length, this relation did not hold (Fig. 3).
The psychological scale of chromatic saturation was transformed into iso-chromatic lines on CIE diagram. In comparison with the Munsell constant-chroma loci, they were more protruding in blue region. As a whole, they were displaced downward with respect to the Munsell's in the condition A and B. This discrepancy almost disappeared in the condition C, however. The isochromatic lines in the condition C significantly expanded, but the rate of expansion was not so great as the expansion of the constant chroma 1^oci at low lightness value in the Munsell system (Fig. 4).