Saturation, Superfluous or Superior?

Of the three basic color perceptions, hue, brightness, and colorfulness, hue has no relative version, but brightness has lightness, and colorfulness has chroma and saturation. Correlates of chroma are widely used in color difference formulae, but saturation currently plays little part in color science and technology. This is perhaps because in many industries flat samples are viewed in uniform lighting for the evaluation of color differences, and in this case chroma is the appropriate contributor for samples of small angular subtense. For samples of large angular subtense, however, a correlate of saturation may be more appropriate to use. In the real world, it is common for solid objects to be seen in directional lighting; in these circumstances saturation is a more useful percept than chroma because saturation remains constant in shadows. In imaging, artists and computer-graphics operators make extensive use of series of colors of constant saturation. In optical imaging, saturation can be an important percept in large dark areas. Recent experimental work has provided a much improved correlate of saturation. Introduction A recently published prestigious book on color science included the statement: " A color's chroma is its col-orfulness. A high chroma color may be described as highly saturated. " There is no further discussion of the differences between colorfulness, chroma, and saturation , and one can only conclude that these matters were something of a mystery to the author, a situation perhaps not too uncommon in the color-science community.