A study on colorimetric errors caused by quantizing color information

When three-dimensional analog signals carrying color information are quantized, quantization errors themselves to do not reflect errors in psychometric color differences because of nonlinear characteristics in the sensitivity of human eyes for colors. The authors convert the quantization errors in the input analog domain to the errors in the uniform color space, the CIE 1976 L*a*b*, so as to evaluate corresponding psychometric quantization errors. The study was conducted for analog signals expressed in the tristimulus values X, Y, Z, and in the primary color signals, R, G, B. The results reveal necessary bits for ADCs as a function of the maximum perceptual color differences between the original and the quantized colors. They also reveal the bit-gain of quantization in the primary color domain against the tristimulus value domain. The study shows that the required minimum amounts of bits for quantization are 12-bit in RGB space and 13-bit in XYZ space to attain quantization color difference of 1.0