Modeling the correlation between ink transfer amount, optical density, and color difference in multicolor offset printing

In this study, the correlation between optical density (D) and color difference (Δ E ab ) was investigated through the variation of ink transfer (Δ G ) efficiency among the CMYK process inks and RGB overprints (R = Y/M, G = Y/C, and B = M/C). The mathematical regression model D = D max (1− e − k .Δ G ) and D = D max (1−e −k.t ) were used to describe the relationship between optical density (D) and ink transfer amount, and ink film thickness (t) and for cyan, magenta, yellow, and black inks, respectively. Statistical analysis (ANOVA, p < 0.001) confirmed the strong correlation between ink transfer and ink film thickness with optical density ( R 2 > 0.90). Correlation between optical density and color difference Δ E ab is the second-order polynomial (y = y 0 + b 1 x + b 2 x 2 ) regression model. The findings emphasize the importance of density control in offset printing to maintain consistent color appearance and minimize Δ E ab across production runs. The mathematical regression models of ink trapping (IT) as a function of the secondary ink volume (IT = IT max (1− e − k .Vink )). The results demonstrate that optical density and color difference are closely governed by ink transfer behavior, and the new trapping model provides a reliable tool for predicting color deviation in multicolor offset printing.