Abstract

The development of the Inter-Society Color Council-National Bureau of Standards (ISCC-NBS) system of color names, based on the standards in the Munsell Book of Color, made it necessary to specify the master standards of this book in fundamental terms. Accordingly, spectral reflection curves were run for each of the 421 master standards on the General Electric recording spectrophotometer at the National Bureau of Standards, using slit widths of approximately 4 millimicrons. Various corrections were applied to these spectrophotometric data in accordance with methods regularly used for such work at the bureau. Colorimetric computations were then made with these data, resulting in tristimulus specifications according to the 1931 ICI standard observer and coordinate system. Four illuminants were used: ICI Illuminants A and C, representative of incandescent-lamp light and average daylight, respectively, Illuminant D (lightly overcast north sky), and Illuminant S (extremely blue sky). The colorimetric specifications of the Munsell standards for all four illuminants are thus given. The trilinear coordinates for the Munsell standards calculated for ICI Illuminant C have been plotted on large chromaticity (x, y) diagrams and constant Munsell chroma lines drawn in. (Similar values obtained by Glenn and Killian at the Massachusetts Institute of Technology in 1935 for Munsell color standards bearing the same hue-value-chroma designations have also been plotted on the diagram and differences between the two sets of data are discussed.) These diagrams serve as means for determining the Munsell notation and thereby the ISCC-NBS color name for any color whose trilinear coordinates and apparent reflectance are given.

© 1943 Optical Society of America

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  1. Figures in parentheses indicate the literature references at the end of this paper.
  2. For YR 2/2. As is to be expected the discrepancies in chromaticity are greatest at the lowest value level.
  3. Differences in Munsell value corresponding to the average differences in Y shown in Table IV are significant only at the lowest values. The difference, ΔY=0.0039, corresponds to ΔV=0.15 at value level 2. It is believed that the NBS data are more reliable than the Glenn-Killian data at these low value levels. For the neutral samples N1/, N2/, and N3/, the Glenn-Killian values of Y are from 0.005 to 0.006 higher than the NBS values given in Table II. Independent check of these samples visually on the Priest-Lange reflectometer gave values lower than the Glenn-Killian values by 0.004, and closely agreeing with the NBS data of Table II.

Other (3)

Figures in parentheses indicate the literature references at the end of this paper.

For YR 2/2. As is to be expected the discrepancies in chromaticity are greatest at the lowest value level.

Differences in Munsell value corresponding to the average differences in Y shown in Table IV are significant only at the lowest values. The difference, ΔY=0.0039, corresponds to ΔV=0.15 at value level 2. It is believed that the NBS data are more reliable than the Glenn-Killian data at these low value levels. For the neutral samples N1/, N2/, and N3/, the Glenn-Killian values of Y are from 0.005 to 0.006 higher than the NBS values given in Table II. Independent check of these samples visually on the Priest-Lange reflectometer gave values lower than the Glenn-Killian values by 0.004, and closely agreeing with the NBS data of Table II.

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Figures (10)

Fig. 1
Fig. 1

Spectral energy distributions of the four illuminants used in deriving the colorimetric data on the Munsell standards. Note: ICI Illuminant A, 2842°K, representative of incandescent illuminants. ICI Illuminant C, representative of average daylight. Illuminant D, representative of lightly overcast sky. Illuminant S, representative of “limit blue sky.”

Fig. 2
Fig. 2

ICI chromaticity diagram showing values of x and y for ICI Illuminant C for Munsell standards of value level 2/.

Fig. 3
Fig. 3

ICI chromaticity diagram showing values of x and y for ICI Illuminant C for Munsell standards of value level 3/.

Fig. 4
Fig. 4

ICI chromaticity diagram showing values of x and y for ICI Illuminant C for Munsell standards of value level 4/.

Fig. 5
Fig. 5

ICI chromaticity diagram showing values of x and y for ICI Illuminant C for Munsell standards of value level 5/.

Fig. 6
Fig. 6

ICI chromaticity diagram showing values of x and y for ICI Illuminant C for Munsell standards of value level 6/.

Fig. 7
Fig. 7

ICI chromaticity diagram showing values of x and y for ICI Illuminant C for Munsell standards of value level 7/.

Fig. 8
Fig. 8

ICI chromaticity diagram showing values of x and y for ICI Illuminant C for Munsell standards of value level 8/.

Fig. 9
Fig. 9

Values of x and y for samples of Munsell value 5/ for illuminats A, C, D, and S. This graph shows the effect of illuminant on the location and shape of the Munsell network.

Fig. 10
Fig. 10

Effect of backing on the spectral apparent reflectance of Munsell samples. The upper curve of each pair was obtained with the sample backed with a white paper (N 9.6/), the lower curve with the sample backed with a black paper (N 1/). Note that no difference in curves caused by difference in backing is apparent for values of reflectance less than 0.6 or at the shorter wave-lengths.

Tables (3)

Tables Icon

Table I ICI tristimulus data for the four illuminants, A, C, D, and S, used in deriving the colorimetric data on the Munsell standards.

Tables Icon

Table II The tristimulus specifications and trilinear coordinates of the Munsell standards for the four illuminants, A, C, D, and S, based on spectrophotometric data obtained at the National Bureau of Standards.

Tables Icon

Table III Effect of backing on colors of Munsell samples. Values are computed from the spectrophotometric curves shown in Fig. 10.