The Characterization Models for Multi-colored CMYKRGB Printing Process

Three models for characterizing 7-ink CMYKRGB printing process, using FM screening for extending color gamut, were derived. The models were the refinements of characterization models described by the authors at a previous TAGA conference. These are two masking types of 2nd order polynomial algorithms (named 2nd-wGCR and 2nd-nGCR) and Cellular Neugebauer equations (named CN). Based on the results of earlier preliminary study, the 2nd model was further modified using some critical, and highly saturated colors having less gray contents. Moreover, an extension of GCR algorithm with the requirement of gray balance was also included in the process of characterization (using 2nd-wG1 CR model). The characterization models derived had been implemented to produce the optimal separations for rendering complex color images. The fidelity of printing reproductions, processed by three 7-ink characterization models (i.e. 2nd-nGCR, 2nd-wGCR and CN) using FM screen method and a conventional 4-ink characterization model using CMYK inks with AM screening method (named Con-CMYK), was also 2assessed by a panel of about 20 observers using the paired-comparison method. The results showed that the 2nd-wGCR employing GCR algorithm performed the best amongst the models tested. It also indicates the importance of gray balance requirement in the characterization of a muti-colored printing process.