AbstractLuminances and saturations of equally bright colors were measured by heterochromatic flicker photometry and a saturation scaling method, respectively. We used 19 dominant wavelengths from 410 to 670 nm and in the purple region, and II excitation purities from 0.0 to 1.0 in 0.I steps for each dominant wavelength, as test stimulus colors. The results show that the luminances of equally bright colors with the same dominant wavelength decrease approximately linearly as the saturation estimates increase for all dominant wavelengths, but the slope of this lumi‐nance‐versus‐satuiation function varies with dominant wavelength. It is implied that the chromatic content of colors differentially contributes to the brightness‐luminance discrepancy depending on the dominant wavelength. We also plotted constant‐luminance loci and constant‐saturation loci in the 1931 CIE x, y and the 19.76 CIE‐u', v' ‐chroma