Color Space and Its Divisions: Color Order From Antiquity to the Present , Rolf G. Kuehni Wiley, Hoboken, N.J., 2003. $99.95 (408 pp.). ISBN 0-471-32670-4
Rolf Kuehni’s Color Space and Its Divisions is an inclusive mosaic of the history of color-order systems, that is, useful arrangements of color, from the time of the preclassical Greeks to the present. One particular scheme invented by Johann Lambert and described in his 1760 book Photometria illustrates how such a system might be used. As quoted in Kuehni, “Caroline wants to have a dress like Selinda’s. She memorizes the color number from the pyramid and will be sure to have the same color. Should the color need to be darker or go more in the direction of another color, this will not pose a problem” (page 55). Lambert’s pyramid is only one of many color-order systems. Using it, as is evident from Lambert’s example, is similar to navigating with a map. Not surprisingly, then, color-order systems are sometimes called color atlases.
A color atlas would seem easier to create than a world map, if only because it requires less travel. However, color atlases are prone to what Kuehni calls fragility (page 309)—their color samples fade and they are difficult to use.
Many of those difficulties are perceptual. Change of illuminant may cause the samples in a color atlas to undergo a perceived “continental drift” or worse. Samples that are distinct under one light may look the same under another, so the continental-drift analogy even includes subduction! Changes in an observer, especially aging, can also lead to such drift effects. In addition, the perceived color of the object one tries to match from the atlas depends on the colors of neighboring objects. If you are unconvinced, try spray-painting a large piece of white paper with yellow fluorescent paint after laying a few coins on the paper to block the paint. When you remove the coins and view the paper in sunlight, the unpainted area will look dark purple. How could Caroline match Selinda’s dress under such conditions?
Mindful of such difficulties, Kuehni traces the development of color-order systems. The earliest system considered is that of Xenophanes, a natural philosopher who lived in the 6th century BCE. Plato and Aristotle proposed one-dimensional scales that didn’t include green or blue. The natural philosopher Avicenna introduced the first multidimensional color scale in the 10th century. The notion of color circles began in the Middle Ages with limited scales that physicians used to classify urine. Another expression of the circle idea, by Sigfrid Forsius, occurred in the 16th century. It was Isaac Newton who brought the circle idea to maturity; he used the spectral colors he got from a prism and identified the center of the circle with white. Kuehni suggests that Newton chose seven basic colors to reinforce an analogy with musical tones, and that he invoked a nonspectral purple to complete his color circle in conformity with the one-octave tonal circle derived by René Descartes.
By now, you may have guessed that Kuehni does not credit physicists with all the answers and breakthroughs in color science. That message, although implicit, emerges eloquently from his arrangement of the mosaic tiles of his history. The book describes a number of color-order systems, many more than just the several most popular, and supports its discussion with more than 500 references. Newton, though, receives less than three pages, and that includes a figure juxtaposing Descartes’s tonal and Newton’s color circles. Hermann von Helmholtz, Hermann Grassmann, James Maxwell, and Erwin Schrödinger together receive about five pages, replete with five figures.
As a retired industrial color expert with a book on colorant formulation to his name, Kuehni understands well the physics of color measurement. However, he views perception rather than physics as the proper reference point for creating a color-order system. He seems reluctant to encumber either his history or the perceptual basis of color order with the ideas of basic colorimetry. For example, only in a single sentence (page 164), does one find a definition of tristimulus values: three weighted wavelength integrals of the light spectrum that represent the stage of vision that commences with a luminous stimulus and ends with the absorption of light by the photopigments of the eye. When Kuehni calls tristimulus space nonlinear (page 347), he clearly is relating that space to the space of perceived colors and not to physical light intensity, because tristimulus coordinates are linear in intensity.
Consonant with the perceptual emphasis, Kuehni enumerates such techniques for quantifying perception as color naming, magnitude estimation, and visual thresholds. Such efforts precede Newton; an interesting application is Francis Glisson’s 1677 scale to classify the color of hair. Kuehni also exhaustively describes attempts to create color-order systems in which equal distances correspond to equal perceived-color differences. His discourse includes many models, some non-Euclidean, that connect light to perceived color. Fortunately, Kuehni defers the detailed model descriptions until after he has defined tristimulus values.
As a physics-oriented color scientist, I find the physical colorimetry to be sketchy and not tutorial. For example, Kuehni’s brief discussion of tristimulus values is not grounded in such general principles as the Grassmann laws, which declare the linearity of color matching and hence the primacy of those values. Indeed, Kuehni doesn’t mention Grassmann’s laws at all. Instead, he launches into the warts of the CIE system that conventionally represents tristimulus values. Although Kuehni’s statements are accurate, they will not teach novices.
In all fairness, Kuehni’s abruptness of style is even handed and perhaps necessary for a book of such a wide historical scope. No mindset, ancient or modern, receives a long discussion. Each contribution, however, is explained briefly and reported traceably. I only hope Kuehni will add an author index to his next edition to increase the value of the large reference list.
My recommendations: Dip into Color Space and Its Divisions as a sightseer, historian, or philosopher. Read it as a color scientist who wants to know who did what first. But do not expect a tutorial.
