Saturation of colored samples at various levels of reflectance

The dependence of saturation on the level of reflectance of colored surfaces was measured by numerical estimation and by matching judgments. Four sets of chromatic samples, one for each hue--blue, 460 nm, green, 510 nm, yellow, 580 nm, and red, 620 nm--within a range between 4% and 65% reflectance, were presented to the observers. The largest changes of saturation were observed at the high and low values of reflectance. The effect is more pronounced for the yellows than for the reds and greens, and relatively less apparent for the blues. For each hue, saturation grows faster at intermediate values of reflectance. The four families of saturation functions permitted us to draw a map of equal-purity contours. There are values of colorimetric purity for which saturation remains constant for all levels of reflectance.