Page:NBS Circular 553.djvu/21

 on the microscope table and a suitable reflectance standard such as an N 9.6/ Munsell paper, a magnesium oxide reflectance standard, or a magnesium carbonate block under the open end of the ocular or camera lucida. Move the slide so that the sample is out of the field of view, adjust the substage condenser, the substage iris diaphragm, or both, of the microscope until the brightness of the slide-liquid-coverglass image on the one side matches that of the image of the reflectance standard on the other. This adjustment should be repeated for each mount studied.

Now move the slide until the sample image touches the dividing line in the middle of the field (fig. 12). Place the appropriate Munsell charts on the table in place of the reflectance standard, and make the comparison for hue as in section 6.1.3 except that when the camera lucida is used, the inner edge of the chart must be slipped under the outer edge of the black cloth. The camera lucida has the advantage over the comparison ocular in that it does not invert the image of the Munsell chart, and also it is less expensive.

6.4.4. The Color Designation. Since the value and chroma vary greatly with the thickness of the sample or with the amount of dye absorbed by it, it is sufficient to determine only the hue of the sample. Estimate the hue to the nearest half-step but judge the value and chroma only accurately enough to determine into which part of the color-name chart the point representing the sample will fall. For example, if the Munsell hue of the sample is 5G, the sample will receive the color name green regardless of the value or chroma; but if the Munsell hue were found to be 3R, samples whose values are above 6.5 would receive the color name pink, but others whose values are below 5.5 would receive the color name red. If the whole color name is desired, proceed as in section 6.1.3.

Color designations may be obtained from chromaticity coordinates (x,y), daylight reflectance Y, derived from spectrophotometric or colorimetric measurements by plotting the (x, y) values on the value chart or charts of the set of Munsell renotation—(x,y) charts [42] corresponding to reflectance Y', and reading the corresponding Munsell renotation. The color designation is then derived in the usual manner from the color-name charts.

The different branches of science, technology, and commerce make use of more or less different color vocabularies some of whose color names (such as Testaceous, Samurai, and Araby) are confusing, or even unknown, to persons in another branch or to the layman on the street. Actually, Testaceous, Samurai, and Araby all refer to grayish reddish orange colors; and, in a similar way, the meanings of all the color names in these vocabularies may be indicatedindidicated [sic] more conveniently and precisely than has hitherto been possible simply by giving for each the ISCC-NBS color designation. As stated by E. N. Gathercoal, these designations are intended to be “sufficiently commonplace to be understood, at least in a general way, by the whole public.” From this basis sprang the idea of including, with the description of the ISCC-NBS method, a Dictionary of Color Names which owes to this method its unique descriptive quality.

This dictionary of color names is comprised of two parts: section 14 is a correlation of all of the color names studied with the ISCC-NBS color designations, and section 15, the dictionary proper, is an alphabetical list of these color names with their corresponding ISCC-NBS color designations. From the former, the color names corresponding to an ISCC-NBS color designation or approximately to each other may be found within the limits of the block-type structure of the ISCC-NBS system. From the latter, the meaning of any one of these color names may be found in terms of the ISCC-NBS system.

Section 14 is a correlation of all of the different color names found in 14 recognized systems of color nomenclature with the 267 ISCC-NBS color designations, each of which has been assigned a serial number to facilitate cross referencing. In other words, each color name listed under an ISCC-NBS color designation is described by a colored sample whose Munsell notation or renotation would fall in the same ISCC-NBS color-name block. Any two color names under one ISCC-NBS designation are approximately equivalent. Other color names nearly equivalent to a given name may be found listed under the ISCC-NBS color designations of adjacent blocks. After each color name in section 14 are given the code numbers or letters identifying the sample by means of which the name is defined, or, if several samples of similar colors are used in the definition, the identification of only one of them is given. The color names in Federal Specification TT-C-595 were collected from a number of federal agencies; so, for identification purposes, the abbreviation of Rh