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 as “the ordinary observing conditions”. Under these conditions the ISCC-NBS color names agree well with common usage. Use of other light sources (such as incandescent-lamp light or light from the mercury arc) will yield object colors not correctly described by these names.

In contradistinction to the color-name charts pub- lished in RP1239 [27] which were based on Munsell book notations, the charts in this revision are based on Munsell renotations. However, the color names resulting from the use of these charts with Munsell book notations will be sufficiently appropriate for all usual purposes. If the precise designation is desired, the conversion from notation to renotation may be read from Final Report of the OSA Subcommittee on the Spacing of the Munsell Colors as in section 6.1.3 [42] and the color name obtained in the usual way.

3. Applications

Aside from the use of the ISCC-NBS system of color names in the National Formulary and the United States Pharmacopoeia for which they were originally developed [29], they are finding increasing use in fields where extreme accuracy or sales appeal are not needed but where a simple, definite, easily understood color designation is desired. Publica- tions in the fields of ceramics [45], chemistry [33, 50], dermatology [2], dyestuffs [46], lights [28], mica [17], interior and exterior painting [3], paper [26], plastics [5, 6], rocks [40], soils [43, 47, 51, 55], stone [31], tex- tiles [54], and general description [1, 18, 25], will give some idea of the type of applications for which these names are used.

4. Logic of Designations

To fulfill the requirements of the problem stated by E. N. Gathercoal, especially comprehension by the public, it was decided to use the simplest color desig- nations possible but to define the individual color ranges so designated as accurately as possible. The hue names were chosen for simplicity and descriptive- ness: red, orange, yellow, green, blue, violet, purple, pink, brown, and olive. Adjectival forms of these hue names are used in the compound designations such as reddish orange, greenish yellow, purplish red. These hue names are preceded by appropriate mod- ifiers (light, dark, pale, deep and so on) also chosen for simplicity and easy understanding. Therefore, the designations for all but very grayish colors consist of a hue name preceded by appropriate modifiers. The designations for very grayish colors consist of a noun (white, gray, or black) with modifiers appropri- ate to the lightness and hue of the colors, such as dark reddish gray or yelloAvish white.

4.1. The Color Solid

In order to understand the color-name blocks used in this system, it will be best to visualize the psy- chological color solid as shown in figure 1. Imagine a grapefruit set on the table so its pithy core is verti- cal. Imagine also that the top of this core is white

WHITE

Figure 1. Dimensions of the color solid.

and that the bottom is black with the intermediate grays in between. Next imagine the spectrum hues stretched around the equator of this grapefruit with the nonspectrum violet to red region filled in with the proper purple colors. Then fill this solid with all colors that a surface may have, thinking of each surface color as a point, with the light colors near the top of the solid and dark ones near the bottom. Grayish colors will naturally be near the core with the more saturated colors near the peel. In such a solid, lightness will be measured up from the base plane of the table, or black, to the top of the core, or white. Saturation will be measured outward from the core with the strongest colors on the peel, and hue will be measured by angle around the core. Fur- ther imagine that all colors falling on one of the vertical planes intersecting in the black-white axis will be of the same hue, all samples falling in one of the horizontal planes through the solid will be of the same lightness, and all colors falling on concentric cylinders about the black-white axis will be of the same saturation.

A. H. Munsell envisioned a system of color stand- ards [10, 13, 30, 35, 36, 48, 49] embracing all colors organized on this plan. Under ordinary observing conditions, the “Munsell value” of a sample corre- lates closely with the lightness of the color perceived to belong to the sample, while the “Munsell chroma” correlates well with the saturation of the color per- ceived to belong to the sample [19, page 47].

Now imagine this Munsell color solid with the primary hues evenly spaced around the equator giv- ing the closed series red, yellow, green, blue, purple and red, with their intermediates. The hue half-way between each two of these primary hues is given a

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