| Abstract:The back trap mottle in the print of different kinds of paper such as color offset newsprint, art paper and single coated paper was evaluated in this paper. Results showed that the optimized conditions of two kinds of newsprint are as follows: ink amount 0.10 mL, printing pressure 650 N, printing speed 0.4 m/s; there exists inconsistent correlation between objective quantitative assessment of mottling and subjective evaluation. Less mottle is obtained with the least ink amount by means of objective quantitative assessment, however, less mottle results are obtained with the medium ink amount when using subjective evaluation. The optimized conditions of the two kinds of single coated paper are as follows: ink amount 0.35 mL, printing pressure 200 N, printing speed 0.3 m/s. The optimized conditions of art paper are different. Results showed that there exists consistent correlation between 2 groups and 4 groups subjective evaluation of mottling. Among the three objective analysis methods, spectrum analysis correlates most closely with the visual results, then the PTS method. And the grey value method correlates at the least. So the spectrum analysis and the PTS method are expected to be the new methods for evaluation of the back trap mottle. |
