Importance of hue: the effect of saturation on hue-chroma asymmetries

Color spaces based on the cardinal color mechanisms, such as DKL, are not perceptually uniform: just-noticeable differences (JNDs) for chroma (and saturation) are larger than for hue, particularly in the orangish and less so in the purplish region. There is evidence that points of equal distance from the achromatic axis are not perceived as equally saturated, suggesting differential scaling between the quadrants. We measured hue and chroma JNDs as well as perceived saturation in the orangish and purplish quadrants of DKL. We calculated chroma-to-hue JND ratios as a function of perceived saturation and found that the ratios were still much higher in the orangish than the purplish quadrant.