Color Uniformity of Digital Presses

This study addressed the color uniformities of digital printing systems. It compared the color uniformities of 28 electrophotographic presses and 9 inkjet presses. The results in this report are coded to protect the identities of the participants.

This study is the third in a series by this research team examining the color uniformity of digital presses. The first study, published in the 2013 TAGA Proceedings, examined the color uniformities of six electrophotographic presses compared to the uniformities of a lithographic press and an inkjet proofing device. The second study (2014 TAGA Proceedings) focused on the color uniformities of large solid areas for seven electrophotographic presses, again compared with an inkjet proofing device.

A 12-page digital test form was designed for this study. The first page included 6 repeats of a 96- color target at different locations on the page. The remaining 11 pages were dominated by large checkerboard patterns providing significant coverage of a single color. Different colors were chosen for each of the pages. All 12 of the test form pages have a cyan, magenta, yellow, and black (CMYK) color bar imaged across the top of the page, � as well as a continuous register track around the perimeter of the page.

The analysis for this study included examination of the color bar to evaluate two things:

• The uniformity of the CMYK colors across the page.
• The consistency of the color bar on the 12 pages of the form.

The second phase of the analysis was to measure the color uniformity of the 11 checkerboard pages. These results shed light on the capacity of the digital presses to uniformly image large solid areas of color.

The third phase of the analysis was to evaluate the color uniformity of the digital presses from the 96-patch color field. This involved reproducing a large number of colors (96) a limited number of times (6) widely spaced across an 11x17-inch page.

The final analysis made in this study was to make subjective comparisons between the register accuracy and the resolution of the digital presses based on photomicrographs taken of sections of the register grid and the Star Targets.