Investigation of color inconstancy and color gamut changes of printed images depending on the standard illuminants

摘要

The main goals of this research are investigation and determination of color balance failure (color inconstancy) of offset printed images expressed by color difference depending on the material used and different standard illuminant conditions. For the experiment, we chose three of the most commonly used in practice illuminants - CIE D50 natural horizon daylight with color temperature 5003 K; CIE F2 cool white fluorescent, 4230 K; CIE A typical Tungsten-filament lighting, 2856 K. A special test form that has been used contains different control strips and measurement components include test chart TC6.02 with about 1000 color patches with different percent combinations of cyan, magenta, yellow and black. The paper, printing inks and printing presses employed in the experiment are some of most commonly used in practice for producing high quality color reproductions. A series of colorimetric and densitometric measurements were performed for different combinations of C, M, Y, K in single, double, triple and quadruple overprint for high tones, middle tones and dark tones. For estimating color balance failure for all the above mentioned measurements there have been calculated the color difference ΔE_(a*b) and CMCCON02 depending on standard illuminants CIE D50, F2 and A. For the first time via experimental research in real production conditions (for offset printing method), 3D and 2D presentations and comparison of color gamuts and color gamut volumes for different illuminants were made. According to the results, CIE A has the biggest color gamut volume and CIE F2 - the smallest one. The results obtained are important from scientific and practical points of view. For the first time a methodology is suggested and implemented for examination and estimation of color shifts by studying a big number of color changes in various ink combinations for different illuminants.