Some New Experiments on the Colorimetric Evaluation of Whiteness

Abstract

In order to confirm and extend earlier work on the colorimetric evaluation of whiteness, different series of white textiles, each of constant reflectance, varying from Y = 96 to Y = 70, are studied. A study of the Gba–Geigy white scale is also included.Earlier predictions about the shape of the equi–whiteness surfaces in the x, y, Y colour space are confirmed and refined. As a result it is established that our original method used as such (using a diagram in the x, y chromaticity chart) or as adapted for numerical computation by Ganz, is applicable to nearly all white textiles, with or without FWAs. Only if shading dyes are used can the colour point transgress the optimum whiteness point corresponding to the reflectance of the material. In such cases it is necessary to use equi–whiteness ellipses around the optimum point, whose position in the chromaticity diagram varies nearly linearly with reflectance.It is also found that catastrophe theory applies to whiteness perception in the vicinity of the optimum whiteness axis in colour space. This means that the whiteness of a given colour in this domain can have a high and a low value, according to circumstances.