Page:Tristimulus specification of the Munsell book of color from spectrophotometric measurements (IA jresv31n1p55).pdf/27

 same hue designations (figs. 2 to 8) are replotted in a single graph, regardless of value level. This is particularly noticeable for the 10 GY, GY, P, 10 RP, and R samples. However, although the maximum (x, y)-difference between the Glenn-Killian and the National Bureau of Standards data is Δx =0.0143 and Δy = 0.0156, inspection of figures 2 to 8 shows that in the great 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 4. 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 4 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

The Munsell notations for chroma and hue may be determined from figures 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 2. By referring to the color-name charts in RP1239, 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