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

Whether a color stimulus appears in the surface-color or in the aperture-co lor mode depends on the luminance relationship between the center color sti mulus and its surround. We investigated how chromaticity of a color stimulu s affected the luminance level at which the appearance of the stimulus chan ged from the surface-color to the aperture-color mode. Mode estimation poin ts were obtained for 10-cd/m(2) color stimuli with different chromaticities presented in the center of a white surround of variable luminance. The col or stimuli tended to appear in the aperture-color mode as purity increased, similarly to the increase of the brightness-to-luminance ratio for equal-l uminance colors. It was also found that the mode-transition sensitivity fun ction was similar in shape to the brightness sensitivity function for 440-6 60-m monochromatic light. Our results indicate that brightness is a determi ning factor for mode transition between the surface-color and the aperture- color modes. We discuss a possible assumption for relationships between bri ghtness and lightness limits of a surface color. (C) 2001 Optical Society o f America.