COLOR GAMUT IN HALF-TONE PRINTING

The study addresses the issue of color in halftone printing. It was motivated by a previous finding, according to which the hues represented by solid printed inks may not be obtained in halftone printing at levels of luminance generated by small and medium single- and multiple-color halftone percentages. To study the color in halftone imaging, model-based simulation, spectral measurements of displays, and thermal transfer printing were used. The focus was on the role of the colorimetric properties of inks and paper. The hue of halftones proved to be very sensitive to the hue difference, given the difference between the CIELab hue angles of the paper and ink. When the difference in hue was close to 90-degrees, deficiencies in the rendering of hue by halftones were most pronounced. A rise in the level of ink luminance exerted a more favorable influence on the color of halftones than a rise of the same magnitude of DELTAE in chroma. The magnitude of observed deficiences in color rendering was assessed by using as criteria the number of reproducible color signal levels and color entropy. With real inks and papers the deficiencies can be significant.