The aim of this study is investigation of gray component replacement (GCR) levels on reflectance spectrum for different overprints of the inks and color reproduction accuracy. The most commonly implemented method in practice for generation of achromatic composition is gray component replacement (GCR). The experiments in this study, have been performed in real production conditions with special test form generated by specialized software. The measuring of reflection spectrum of printed colors, gives a complete conception for the effect of different gray component replacement levels on color reproduction accuracy. For better data analyses and modeling of processes, we have calculated (converted) the CIEL<sup>*</sup>a<sup>*</sup>b<sup>*</sup> color coordinates from the reflection spectra data. The assessment of color accuracy by using different GCR amount has been made by calculation of color difference ΔE<sup>*</sup> ab. In addition for the specific printing conditions we have created ICC profiles with different GCR amounts. A comparison of the color gamuts has been performed. For a first time a methodology is implemented for examination and estimation of effect of GCR levels on color reproduction accuracy by studying a big number of colors in entire visible spectrum. Implementation in practice of the results achieved in this experiment, will lead to improved gray balance and better color accuracy. Another important effect of this research is reduction of financial costs of printing production by decreasing of ink consumption, indirect reduction of emissions during the manufacture of inks and facilitates the process of deinking during the recycling paper.
The paper presents investigation of the effect of different values of total area coverage of inks (TAC) on reflection spectra and color gamut. Total area coverage is a key factor for achieving of maximal volume of color gamut. The reflection spectra of color surfaces in entire visible spectrum are used for determination the effect of different values of TAC. For study the effect of TAC values on color gamut, we have used special test form that contains many components and test charts with over 1500 color patches. According to measurement of reflectance spectrum of test charts, we have compared the color gamuts with different values of TAC to obtain comprehensive information of all colors, which could be reproduced in the specific conditions. In addition we have converted the reflection spectra data to CIE L<sup>*</sup>a<sup>*</sup>b<sup>*</sup> coordinates, and we have calculated the color difference ΔE<sup>*</sup> <sub>ab</sub> to determine the effect of TAC on color reproduction accuracy. The main goal of this study is development of methodology, which gives objective and analytical assessment, for determining the optimal value of total area coverage (TAC). A practical implementation of the correct and optimal value of total area coverage should improve the printability, better ink layers adhesion, biggest number of trapping values and reduce the quantity of process inks. The optimal value of the TAC determined by this new methodology helps to achieve a significant reduction of ink cost and a maximal color gamut volume, i.e. improve the quality of printed image and reduce financial costs.