22. Locate Color Tolerance for Mapping Mode Based on Human Visual and Color Difference Formula

When color digital images output on substrates, color space is converted, causing the color differences between prints and electronic manuscript. In order to locate the way to map and relatively corrected error range, the original is converted to 4 CMYK modes through the intentions of perception, saturation, relative colorimetry, and absolute colorimetry, respectively. Adobe Photoshop (Ps) software is used to draw a–b, a–L, and b–L color gamut graphs to determine the spatial domain of each color tolerance. The background is center color contrasting with the other color. Thus, the graphs can be straightly detected by human eyes easily. In complex calculation of formula, experiment successfully draws color difference ball, chroma difference cylinder, and hue difference parabolic in Lab space. It really helps figure out the tolerance range of different mappings and prints. The above numerical relationship is fed back to the process of color gamut conversion and image reproduction. Then, color measurement and calculation are further conducted to verify the accuracy of color gamut conversion.