A study on colorimetric errors caused by quantizing chromaticity information

Quantization errors resulting from a linear analog-to-digital converter (ADC) are represented by a uniform sawtooth. When three-dimensional analog signals carrying chromaticity information are quantized, the quantization errors themselves do not reflect errors in psychometric color differences because of the nonlinear color sensitivity of human eyes. An attempt is made to convert the quantization errors in the input analog domain to the errors in the uniform chromaticity coordinates so as to evaluate corresponding psychometric quantization errors. The study is conducted for analog signals expressed in the tristimulus values, X, Y, Z, and in the primary color signals, R, G, B. The result of the former is applicable to digital colorimeters, and the latter is important for color sensors like video cameras and is applicable to measurements using digital video signals. The results are used to determine necessary bits for ADCs as functions of the maximum perceptual color differences between the original and the quantized colors