Color by Rolf G. Kuehni

Author:Rolf G. Kuehni
Language: eng
Format: epub
ISBN: 9781118173848
Publisher: Wiley
Published: 2015-07-13T04:00:00+00:00

FIGURE 6.9 Basic types of optimal object reflectance functions: a and b with one, c and d with two transitions between zero and perfect reflectance.

FIGURE 6.10 Two views of Luther’s optimal object color solid (Luther 1927). The solid is based on two linear chromatic opponent functions and a lightness function derived from König’s fundamentals.

Shortly after the CIE colorimetric system had been established, such solids were calculated by MacAdam (1935) for optimal object colors viewed by the standard observer in daylight illuminant C (an early version of average daylight) and in tungsten illuminant A erected over the CIE chromaticity diagram. The result for illuminant D65, calculated later, is shown in Figure 6.11. All possible object color stimuli for this illuminant and the 2° standard observer fall on or within the surface. An optimal object color solid in cone space was shown in Figure 5.14. In Figure 6.11, the central axis represents achromatic colors with zero luminous reflectance on the plane and luminous reflectance 100 on top. While instructive of the geometrical realities of the object color stimulus solid, this space, like the diagram it is based on, has no relationship of practical value to color appearance.

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