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 (10) H. T. Wensel, D. B. Judd, and Wm. F. Roeser, “Establishment of a scale of color temperature,” J. Research Nat. Bur. Stand. 12, 527 (1934); RP 677

(11) Dorothy Nickerson, ‘‘Artificial daylighting for color grading of agricultural products,” J. Opt. Soc. Am. 29, 1 (1939).

(12) Dorothy Nickerson, ‘Artificial daylighting studies,” Trans. I.E.S. 34, 1233 (1939).

(13) K. S. Gibson, ‘“‘Approximate spectral energy distribution of skylight,”’ J. Opt. Soc. Am. 30, 88 (1940).

(14) Dorothy Nickerson, ‘Computational tables for use in studies of artificial daylighting,’’ Agricultural Marketing Administration (mimeographed).

(15) K. S. Gibson and H. J. Keegan, “On the magnitude of the error resulting from fluorescence in spectrophotometric measurements,” J. Opt. Soc. Am. 28, 180 (1938).

(16) “Preparation and colorimetric properties of a magnesium oxide reflectance standard,” Letter Circular Nat. Bur. Stand. LC-547 (March, 1939).

(17) K. S. Gibson and H. J. Keegan, “Calibration and operation of the General Electric recording specatrophotometer of the National Bureau of Standards,” J. Opt. Soc. Am. 28, 372 (1938).

(18) K. S. Gibson, “Survey of spectrophotometers,”’ Paper Trade Journal 111, 135 (1940).

(19) Raymond Davis and K. S. Gibson, “Filters for the reproduction of sunlight and daylight and the determination of color temperature,’ Bur. Stand. Miscellaneous Pub. No. 114 (1931); M114.

(20) Lila F. Knudsen, ‘‘A punch card technique to obtain coefficients of orthogonal polynomials,” J. Am. Stat. Assoc. 37, 496 (1942).

(21) Dorothy Nickerson, ‘‘Use of ICI tristimulus values in disk colorimetry,” a preliminary report. U. S. Department of Agriculture (May, 1938).

(22) ‘Photoelectric ‘colorimeters.’ " Letter Circular NBS, LC-545 (March, 1939),

(23) J. A. Van den Akker, ‘‘A survey of abridged spectrophotometers,” Paper Trade Journal 111, 142 (1940).

JOURNAL OF THE OPTICAL SOCIETY OF AMERICA VOLUME 33, NUMBER 7    JULY, 1943

Tricrhomatic Specifications for Intermediate and Special Colors of the Munsell System

, Interchemical Corporation Research Laboratories, New York, New York, , Food Distribution Administration, U. S. Department of Agriculture, Washington, D. C., , Color Consultant, New York, New York

HE Munsell concept of hue, value, and chroma (1), (2) and the Munsell notation for recording colors in terms of numerical scales of these three attributes, are daily proving themselves useful in color work (3), (4). The usefulness of the Munsell charts in color measurement grows in direct ratio to the accuracy and availability of standard colorimetric data that become available regarding the colors on those charts. Actually no one color is more a “Munsell color” than any other, but the charts are devised so that selected points of intersection in the color solid are illustrated, and these are often called “Munsell colors.”

The 1929 edition of the Munsell Book of Color (5) contained chips representing 10 major hues on value levels 2/ to 8/, at all even steps of chroma, and 10 hues intermediate between these major hues on value levels 2/ to 8/, at even steps of chroma beginning with /4 chroma. These are the standard colors for which I.C.I. tristimulus values and trilinear coordinates have been reported for Illuminant C by Glenn and Killian (6), for Illuminants A, C, Macbeth 7500°K, and a limit blue sky. by Kelly, Gibson, and Nickerson (7).

Because many people find that direct reference to color charts is the simplest method for obtaining color notations, and because many people are not able satisfactorily to interpolate between hues that are as far apart as one twentieth of the hue circuit, “Munsell colors” now appear in an additional series of 20 hues, each of the 20 new hues being intermediate between a pair of the earlier standard 20 hues. All /2 chromas omitted in the 1929 edition have been added. These colors total 561 samples (in addition to the 421 samples of the standard series). In addition to these colors for new charts to be inserted in the early series, several other series of colors have been made available for special purposes. Thus, there is a series of 100 hues at 5/5, 50 hues at their maxima chromas, a 50-step value scale, a 20-step value scale, a series of pinks, of browns, and others. Each of these series becomes more useful as standard I.C.I. colorimetric data become available for it.

The authors have therefore measured these colors spectrophotometrically and have com-