Abstract

Automated color measurement systems have become significant components of offset lithographic printing presses for better process control and reduced job waste. In Europe, printers have broadly adopted polarized densitometry, which is uncommon in US standard operating procedures. It is recognized that some European press manufacturers provide automated color measurement instrumentation limited to polarized density readings. Introducing polarized densitometry into an environment where unpolarized densitometry is utilized can be problematic. The increasing significance of this issue has motivated print professionals to look for a solution. 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 polarized and unpolarized 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 also 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 showed fixed bias by means of the computed p-values. The primary conclusion of this study is that a single conversion method is not reliable in all contexts. The more variables that need to be accounted for in conversion, the less reliable the method becomes. The methodology for converting polarized to unpolarized readings presented in this study may be practical within the current parameters, but practitioners should take caution when applying the same or similar methods. Further research is encouraged using various inks, substrates, printing processes, and other possible conditions. Such studies could validate the current research while further examining the topic.

Publication Date

8-2021

Document Type

Thesis

Student Type

Graduate

Degree Name

Print Media (MS)

Advisor

Bruce Leigh Myers

Advisor/Committee Member

Bilge Nazil Altay

Campus

RIT – Main Campus

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