Luminance of Equally Bright Colors*

An analysis has been made of the Y values, or luminances, of 342 colored filters which had been previously matched in brightness by direct visual comparison. The CIE diagram was partitioned into 20 zones and the average luminance calculated for the colors in each zone. The results show regular shifts in the average luminance values over the CIE diagram. Supplementary experiments support the principal findings. In general, the data agree with other recent studies which show that, for colors of equal brightness, saturated colors require less luminance than desaturated ones. However, there is a reversal of this trend in the yellow area since the point of maximum luminance for a given brightness occurs there. The latter finding agrees closely with recent predictions by MacAdam based on his model of visually homogeneous color space.