Abstract
Heterochromatic brightness matches with checkerboard patterns made up of a white reference and a chromatic test element for various element sizes from 3′ to 2°30′ square and with a 5° bipartite field were carried out with a color cathode-ray tube. The brightness-to-luminance (B/L) ratios of six chromatic stimuli were obtained, and the brightness additivity for the mixture of red and green was tested. When the reference and test elements were juxtaposed without a gap, the B/L ratio of the test chromatic stimulus decreased with decreasing element size. Brightness additivity failed for an element size of 30′ and a 5° bipartite field. Brightness additivity held for a small element size of 3′. When the reference and test elements were separated by a gap 3′ in width, the B/L ratios were generally greater than unity regardless of element size. Under these conditions, the brightness additivity also failed for the smallest, that is, the 3′ element size.
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