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 majority of cases there is good agreement between the two sets of data. Further effort to resolve the differences would seem unwarranted.

2. Differences in the average values of Y obtained in the two investigations are shown in Table IV. The greatest differences are at the extremes. That for Munsell value 8 may be caused partially by the differences in backing. That for Munsell value 2 may indicate a real instrumental difference relating to the zero readings of the respective instruments; none of the 33 individual differences going into this average is negative. While the individual differences on which the values of Table IV are based reached a maximum of 0.036 (sample P 7/2), the final average value of +0.002 for all of the data is very small.

VI. DERIVATION OF ISCC-NBS COLOR NAMES FROM ICI TRISTIMULUS DATA

The Munsell notations for chroma and hue may be determined from Figs. 2 to 8 for any color whose chromaticity falls within these diagrams by plotting its trilinear coordinates on the appropriate value-level diagrams and estimating the relative position of this point with respect to the points representing the nearest samples of constant hue and the nearest lines of constant chroma. The Munsell value of the color is found by interpolation or extrapolation between the values of apparent reflectance (Y) of the Munsell standards for Illuminant C in Table II. By referring to the color-name charts in RP 1239, the ISCC-NBS color name descriptive of that color will be found. Likewise in disk colorimetry (21), given percentages of a certain set of disks may be transformed into trilinear coordinates, plotted in a similar-manner, and the corresponding color name found. Thus the ISCC-NBS color name for a color may be found by the use of any spectrophotometer or colorimeter (22), (23) whose resultant values may be transformed into data based on the ICI standard observer and coordinate system. Likewise, any color system may be used as a comparison standard if the trilinear coordinates of each sample in that system are plotted on the (x, y)-diagrams and the ISCC-NBS color name determined through conversion to the Munsell notation.

VII. ACKNOWLEDGMENT

The authors wish to express their appreciation to Leo G. Glasser, Harry J. Keegan, and Margaret M. Balcom for running the spectral reflection curves on which the data of the present paper are based, and to Davis H. Wilson for directing the tabulating and statistical work on the Hollerith cards. They also wish to acknowledge their indebtedness to the late Walter T. Spry, former manager of the Munsell Color Company, and to Mrs. Blanche R. Bellamy, present manager of the Munsell Color Company, who have seen that nothing was lacking in samples or assistance to make this project a success.

VIII. BIBLIOGRAPHY

(1) Deane B. Judd, “Color-blindness and anomalies of vision,” J. Soc. Mot. Pict. Eng. 26, 616 (1936).

(2) “Color names in the United States pharmacopoeia and in the arts, sciences, and industries.” Supplement to the Circulars of the Committee of Revision, U. S. Pharmacopoeia (1920-1930).

(3) Report of Committee on Measurement and Specification for the year 1933. Submitted to the InterSociety Color Council by I. H. Godlove, Chairman.

(4) Deane B. Judd and Kenneth L. Kelley, “Method of designating colors,” J. Research Nat. Bur. Stand. 23, 355 (1939); RP 1239.

(5) Kenneth L. Kelly, “Instructions for determining the color names for drugs and chemicals,” Bull. Nat. Form. Comm. 8, 359 (1940).

(6) Dorothy Nickerson and Sidney M. Newhall, “Central notations for ISCC-NBS color names,” J. Opt. Soc. Am. 31, 587 (1941).

(7) Munsell Book of Color (The Munsell Golor Company, Baltimore, 1929).

(8) Papers on the Munsell color system, J. Opt. Soc. Am. 30 (1940):

Dorothy Nickerson, “History of the Munsell color system and its scientific application,” p. 575.

John E. Tyler and Arthur C. Hardy, “Analysis of the original Munsell color system,”’ p. 587.

Kasson S. Gibson and Dorothy Nickerson, “Analysis of the Munsell color system based on measurements made in 1919 and 1926,” p 591.

James J. Glenn and James T. Killian, “Trichromatic analysis of the Munsell Book of Color,” p. 609.

Sidney M. Newhall, “Preliminary report of the O.S.A. subcommittee on the spacing of the Munsell colors,” p. 617.

(9) Deane B. Judd, “The 1931 ICI standard observer and coordinate system for colorimetry,” J. Opt. Soc. Am. 23, 359 (1933).