Research on Spectral Reflection Characteristics of Overprinted Color Inks and the Numeric Compensation to the Theoretical Model

The trapping of several color inks on substrate is a general phenomenon in multicolor printing. As fundament of color reproduction, the spectral characteristics of mono-color ink and of overprinted color inks are close related with the color reproduction. Theoretically, the spectral reflectance of overprinted color inks can be obtained from spectral reflectance of inks and of substrate. But the error appears, because some influences from ink, paper and other external conditions exist. Based on the measured spectral reflectance of Cyan/Magenta/Yellow/Black ink, of paper and of the overprinted inks, the spectral difference between measured and the theoretical data is compared and analyzed. The spectral difference data is transformed to DCT coefficients and filtered. Applying the compensation data from inverse DCT curve, the corresponding color errors (ΔE) are very small.