Page 65 - RoadCem Manual - PCT BV

Figure 4.13 Different soil types and profiles.
In the early 1900’s a study was done to make color description easier. The method devised used the artist’s color well. Each pie wedge represented a particular spectral wavelength or HUE (R=Red etc.) These wedges could be further divided into smaller sections (1R = 10% Red, 10R = 100% Red). Typically only the 25, 50, 75 and 100% are used (2.5, 5, 7.5, and 10). The HUE does not tell the whole story. Shading (value) and purity or intensity (chroma) was then added. A measure of lightness or darkness was then added. Value refers to how light or dark the color is (gray scale). Value indicates the degree of lightness or darkness of a color relative to gray. Value extends from pure black (0) to pure white (10) and is a measure of the amount of light that reaches the eye, gray is perceived as about halfway between black and white and has a value notation of 5. Lighter colors have values between 5 and 10; darker colors are between 5 and 0. Chroma is the relative purity or strength of the spectral color. Chroma indicates the degree of saturation of neutral gray by the spectral color. Chromas extend from 0 for neutral colors to 8 as the strongest expression of the color.
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