Brightness, not luminance, determines transition from the surface-color to the aperture-color mode for colored lights

Whether a color stimulus appears in the surface-color or in the aperture-color mode depends on the luminance relationship between the center color stimulus and its surround. We investigated how chromaticity of a color stimulus affected the luminance level at which the appearance of the stimulus changed from the surface-color to the aperture-color mode. Mode estimation points were obtained for 10-cd/m2 color stimuli with different chromaticities presented in the center of a white surround of variable luminance. The color stimuli tended to appear in the aperture-color mode as purity increased, similarly to the increase of the brightness-to-luminance ratio for equal-luminance colors. It was also found that the mode-transition sensitivity function was similar in shape to the brightness sensitivity function for 440–660-m monochromatic light. Our results indicate that brightness is a determining factor for mode transition between the surface-color and the aperture-color modes. We discuss a possible assumption for relationships between brightness and lightness limits of a surface color.