<title>Measuring small color differences in the nearly neutral region by 3CCD camera</title>

Abstract

A method to evaluate the discrimination capability of a camera to measure small color differences in the nearly neutral region is proposed. We focus on the camera's performance in the nearly neutral region of the color space because: it represents a challenge for the instrument (these colors entail a similar stimulation of the RGB channels) and, second, these colors concentrate industrial interest, particularly related to materials for clothing or decorating. The method proposed has two stages. Firstly, we determine the appropriate working conditions of the acquisition system (SONY DX-9100P camera). Secondly, we select two sets of matte Munsell samples, regularly distributed in the Hue circle with low Chroma and Values. These two sets of samples are the very pale color and the dark grayish color sets. Each selected chip is compared with all its nearest neighbors of the Munsell color system under D65 illumination. CIELAB and CIEDE2000 formulae is used to estimate color differences. All the color differences are separately evaluated in pairs by the camera and by a reference instrument (spectroradiometer Photo-Research PR-715). We test the reliability of the camera's performance by comparing the results obtained by both the camera and the spectroradiometer.