Whiteness as a color-classification problem

Abstract

Colors called "white' are found in a small but yet not sharply defined region of the color space. The main characteristics of a white sample are high ligthness, tristimulus value Y > 70 and low saturation, excitation purity p <jo.1 and it is usually assumed that the reflectance spectra are continuous. In our study we measured 24 white samples, Ciba Geigy Plastic White Scale and white ceramic plates, with an acousto-optic color spectrometer and tested several whiteness formulas, based both to conventional color coordinate definitions and to statistical pattern recognition and classification methods, to find out the best whiteness formula for quality inspection and assortment. Each sample was measured 20 times in the same geometry (0/45) using normal tungsten halogen lamp as a light source, and the reflectance spectrum was measured from 400 nm to 700 nm with 5 nm intervals in order to achieve high accuracy for color determination.