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 C recommended by the CIE [53] as representative of average daylight is to be used.

6.1.3. Determination of a Munsell Notation or Renotation. Select the two adjacent Munsell constant-hue charts between which the hue of the sample falls. Place these on each side of the sample and cover each with a small neutral gray shield, or if using the large triple-aperture shield (shown in fig. 5), place them under the holes in the side flaps and the sample under the central opening. The Munsell hue, value, and chroma notations for a sample are found by interpolation or extrapolation among the standards of the Munsell charts; most operators prefer to estimate first the value, then the chroma., and finally the hue. Tins is done as follows: look at the three colored rectangles (1 sample and two standards) and see whether the sample is lighter or darker than the standards. Move the chart whose hue is nearer to that of the sample up and down from one value level to another and find the two values between which that of the sample falls. Next esti- mate to the nearest tenth of a value step the value of the sample relative to these two levels. Record this number in front of a shilling mark as, for example, 3.0/ or 6.2/.

Then move the charts sideways so as to present successively colors of the same Munsell hue and value but of different chroma, and by similar inter- polation determine the Munsell chroma of the color. In this comparison pay chief attention to the Munsell standards having values nearest that of the sample, and secondary attention to those next nearest. Although all Munsell samples of the same chroma notation are intended to yield in daylight color perceptions of the same saturation, sometimes a slightly different estimate of chroma will be obtained by comparison with the standards of the next nearest value. In such an instance, report an average nota- tion for chroma. Note that there are two chroma

steps between each two adjacent columns of Munsell samples. Estimate the chroma to the nearest fifth step and record this number after the value notation and the shilling mark, as, for example, 3. 0/6.0 or 6. 2/4. 6.

Now with the corresponding Munsell standards of value and chroma closest to those of the sample showing through the apertures of the shield, estimate the hue of the sample relative to that of the two Munsell charts. Remember that each two adjacent charts are two and a half hue steps apart. Record the hue estimated by this interpolation to the nearest one-half step in front of the value/chroma designation and separated from it by a space; for example, 7Y 3. 0/6.0 or 9.5YR 6. 2/4. 6. If the value and chroma of the sample do not correspond very closely to those of any of the Munsell standards, it is advisable to repeat the interpolation for hue with the next closest pair of standards and take an average nota- tion for the hue.

Check the Munsell notation, particularly hue and value, with the charts interchanged.

For most color descriptions, the ISCC-NBS color names derived from the Munsell book notations as determined above are sufficiently applicable. If greater accuracy is demanded, determine the chroma- ticity coordinates, x, y and daylight reflectance Y corresponding to this Munsell notation from figures 2 to 8 in the paper by Kelly, Gibson, and Nickerson [30]. From these values, determine the Munsell renotation from figures 1 to 9 of the paper by New- ha.ll, Nickerson, and Judd [42],

6.1.4. The Color Designation. After the Munsell notation for the sample has been determined, select the color-name chart referring to the Munsell hue of the sample (see Munsell hue designation near the upper right hand corner of the color-name chart). Plot the value and chroma of the sample on this chart and record the name of the block in which this point falls as the color designation of the sample. If, however, the point falls on a hue, value, or chroma boundary, the names of all of the blocks touching the point apply to the sample. Any one, two or all of the names may be used as the designation of the sample depending on the type of name desired.

Different degrees of precision of designation are possible under this system. For more precise designa- tion than is possible by color names alone, specifica- tion by the Munsell notation itself can be used. For the colors of solids, powders and some colored liquids or glasses, the complete color designations (hue name and modifiers) defined herein should be used. For the colors of microscopic structures, most liquids and most chemical tests, the hue names alone are sufficient. Where two or more hue names are used, they should be arranged in sequence according to the Munsell hue sequence (red-yellow-green-blue-purple-red).

6.1.5. An Example. Suppose that the hue of the sample falls between the 7.5YR and 10YR charts and that its value falls between the 7 and 8 value levels, but nearer the 7, and is estimated as 7.2. Suppose further that its chroma is found to be 6