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The advantages of a quasi-psychological system, calibrated by physical measurements, are obvious after a little thought. Any set of comparator standards has as its chief advantage the direct presentation of exemplars of the colors in question, so that no demands are made on the color memory, which is notoriously bad, or the imagination. With its aid colors may be so specified that we may know at once and unambiguously whether one is lighter or darker, more vivid or grayer, or redder or bluer, and how much, than another. Further, it is only by the use of a language of specification of color couched in the terms of such a method that we are able to reach a solution of most problems which are problems of color per se. Spectrophotometry is ideal in most problems in which our primary interest is not the color, but the physical properties of an object or material, as those problems of plant control of the chemical composition, where color is used merely as an indicator of quality. On the other hand, where we have such problems as the study of “fading,” the harmonious relation of the color of stock, initial lettering, and print in advertising, the control and selection of the color of lacquers, enamels and paints; and in all cases of liason between the links of the chain, customer, manufacturer, superintendent, foreman, worker; the need of a visually descriptive method of specification is imperative. If a realization of the differentiation of these two classes of problems were more generally effected, it would help greatly in the clarification of many industrial problems. On the theoretical side, the advantage of a complete quasi-psychological system is that it is the final link in the complete correlation and inter-translation of the diverse languages of color, from the extreme physical to the extreme psychological. Chiefly on the practical, but also on the theoretical, side, accurate calibration of standards carries over to the method the main advantages of spectrophotometry, precision and reproducibility, to a considerable degree. When judging this augmented precision, a fact must be recalled. The great possible precision of purely physical methods, when applied to color specification, is only too often a pseudo-precision. In many cases, even when the spectral reflection curves of two colors differ from each other at all points by only the thickness of the pen mark, the color difference is clearly perceptible under the proper conditions; on the other hand, cases may occur where the curves differ from each other by a thumb’s width at some points when the colors are actually indistinguishable.
These measurements, briefly described below, will be reported in a subsequent paper.
Unpublished material of the Munsell Research Laboratory and the National Bureau of Standards (N. B. S. Test 46,045). The measurements were conducted under the direction of Dr. K. S. Gibson and the use of the results for the present check was suggested by Dr. D. B. Judd.
This work extended over a course of several years, during which time the standard neutral lights in general use underwent changes.
Table I Hue and chroma of 32 colors determined by two independent methods.