The world of colour

The world of colour - David Katz

This book is an abridged translation of the second edition (1930) of Der Aufbau der Farbwelt. It begins with a differentiation of the modes of appearance ( Erscheinungsweise) of colors, into "surface colors"—definitely localized in the surface of objects; "film colors"—vague and indefinitely localized like the color of the sky; transparent and voluminous colors; luster, and glow. Characteristic object colors, the "genuine colors" of objects, are constituted by their surface colors seen under moderate daylight illumination, when the micro-structure of the surface is fully displayed. But all these modes of appearance can be reduced to that of film color by viewing them through the aperture in a reduction screen. Color constancy, which depends on the differentiation of object color from the effects of the general illumination, is thus destroyed by reduction. A light gray surface may, under reduction, have the same brightness as a dark gray one; but when the reduction screen is removed, the former will appear light gray in color quality, but of less "pronouncedness" ( Ausgeprägheit) and less illuminated than the other surface, which has a dark gray color quality. The general illumination of the field is estimated from its total insistence ( Gesamt-eindringlichkeit), which is determined by the total amount of light it reflects to the eye. Since variations in intensity of illumination range through 1: 36,000 while variations in brightness of surface color (dead black to brightest white) range through 1: 60, variations in total insistence depend more on the former factor. Hence they are interpreted as variations in general illumination with constancy of surface color, as long as surface or object colors can be perceived as such.