Investigating the agreement between polarized and unpolarized densitometry in offset lithography printing

Abstract

Automated color measurement systems have become significant components of offset lithographic printing presses for better process control and reduced job waste. Some European press manufacturers are known to offer automated color measurement equipment that is confined to polarized density readings, which is uncommon in US. Introducing polarized densitometry into an environment where unpolarized densitometry is utilized can be problematic. Print professionals are on the lookout for a solution that is evidenced by a recent feature in a post from the IDEAlliance G7 Professionals forum seeking for a methodology to convert polarized to unpolarized readings. The present study applies the Bland-Altman method together with other statistical analyses to determine if a conversion between polarized and unpolarized densitometry can be established within a limited set of parameters. Three spectrodensitometers were used to record densitometric readings of wet and dry process inks on coated and uncoated drawdown proofs. The results showed that coated papers had significantly less variation between instruments compared to uncoated papers. Wet inks had more minor variations compared to dry inks. Furthermore, pure difference values and a Mann-Whitney U test indicated differences between unpolarized and polarized densitometric readings in all cases. Finally, t-tests performed on the resulting difference data for both unpolarized versus polarized and unpolarized versus predicted polarized that showed fixed bias by means of the computed p-values.

Impact of optical brightening agents on alkali‐based inks in packaging: A comparative study on color accuracy

“…This process ensures the ink is evenly distributed and results in a high‐quality print. A similar process was followed by other researchers for proofing on Little Joe 19 . The inks are printed on two separate substrates and labeled as first pass (1st pass) and second pass (2nd pass).…”

“…A similar process was followed by other researchers for proofing on Little Joe. 19 The inks are printed on two separate substrates and labeled as first pass (1st pass) and second pass (2nd pass). Most of the inks were within target delta E (ΔE 00 ) of less than three based on the 2nd pass, except rubine red on non-OBA paper.…”