The Adams chromatic-value diagram has several advantages, including the small effect of Munsell value on the constant-chroma loci, permitting rapid interpolation between value levels; also, chromaticity-differences and Munsell notations may be determined directly from the tristimulus values X, Y, Z. But the disadvantages are that the constant-chroma loci of the Munsell Renotation colors, which yield the best data available to us, have an ovoid form; and the neutral-to-yellow radius is about 72 percent longer than the neutral-to-purple blue radius. The Hunter diagram and one recently proposed by Judd are badly flattened in the yellow region. Various transformations of the Adams variables to yield near-circular contours have now been investigated along with other transformations and more direct studies. The author is concerned mainly with rapid evaluation of color differences direct from X, Y, Z. Because of the noncongruity of the Renotation contours, compromises must be made to achieve optimum circularity, hue spacing, straightness of constant-hue lines, “linearity,” constancy of radii, and speed of transformation. For the best of the transformations studied, a table has been prepared to permit immediate reading off of new variables h and v. Two columns contain h for positive and negative values of Adams “H”=VX−VY; six more contain values of v for values of Adams “V”=VZ−VY for three diagrams, one each “corrected” for colors of chroma 10, 6, and 3, respectively. These are used in the chroma ranges 0–4, 4–8, and 6–16, respectively. When two greatly different chromas are involved, a new color-difference formula has been derived and tested. While stressing circularity, straightness of hue lines and speed, fairly good results in respect to the other criteria of merit have been obtained. The method is illustrated by application to a series of fadings previously judged visually by a committee of 12 textile-mill men; and the improvement over the Adams method is shown.
© 1952 Optical Society of AmericaFull Article | PDF Article
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