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Practical testing of irradiance-independent camera color calibration

The procedure of camera color calibration ensures accurate and repeatable acquisition of scene colors. The main process of calibration procedure is the color transformation from camera RGB color space to device independent color space, such as CIEXYZ or CIELAB. Typical calibration procedure assumes the uniformity of irradiance across the whole scene, but such assumption is difficult to achieve. Spatial changes in irradiance are typical for indoor and outdoor light conditions. The problem of color calibration under non-uniform lighting was researched by, e.g., B. Funt and P. Bastani. In the present article, their calibration procedure was tested together with the classic approach to camera calibration. Based on these experiments a modification was proposed, in which RGB image values are scaled accordingly to the results of additional measurements. This modification allows to obtain, in conditions of spatially nonuniform scene illumination, lower values of color differences ΔE * ab and ΔE00 than in cases of classic method and FuntBastani method.