Role of Chromaticity Difference in Color Graininess Judgments*

Abstract

It is known that, for black-and-white materials, the threshold “graininess” of a random pattern of dots on a background of a different luminance varies in a uniform manner with the difference between the log luminance of the dot and that of the background. For similar samples prepared with dots of one color on a background of a different color, it was found that this relationship does not hold. Data are presented showing that a correlation exists between ΔE and graininess, where ΔE=[(ΔD)2+K(ΔC)2]12. Here, ΔD is the log luminance difference and ΔC the chromaticity difference (as measured on a uniform chromaticity scale) between the dots and the background. As a preliminary to the main experiment, the visual brightness of the 48 samples was measured for a 2-degree field, and the corresponding luminance values were computed. All the differences were erratic and were within the limits of experimental error.