Ink Trapping Assessment Based on Reflectance Spectra Analysis of Overprint

ABSTRACT

In this study, a spectral ink trapping evaluation approach based on ΔE _ab color difference between ideal and real colors was developed and systematically compared with the conventional Preucil, Ritz, and Brunner trapping formulas. The results indicate that the calculated (ideal) reflectance spectra show excellent agreement with the measured (real) data. Statistical parameters such as the root mean square error (RMSE) and standard deviation (Std. Dev.) demonstrate that the proposed model provides accurate predictions across different ink volume ratios and printing sequences. The goodness‐of‐fit coefficient (GFC) values are extremely high (mostly > 0.99), confirming that the calculated spectral shapes closely match those measured by the spectrophotometer. The results showed strong inverse linear correlations between ΔE _ab and conventional ink trapping values for most overprint systems. The obtained results demonstrate the higher sensitivity of the spectral ink trapping approach based on ΔE _ab compared with the conventional Preucil, Ritz, and Brunner formulas. The proposed spectral trapping method demonstrates promising potential for quality control, process monitoring, and color reproduction in offset printing.