A Theoretical and Experimental Comparison of the GRACoL and ISO Approaches to Press Characterization and the Data Sets Produced


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Greg Radencic, Joe Suffoletto, and Dr. Mark Bohan


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There are many methods that can be used to set of the print appearance on a press. A proof and print calibration has been proposed by the GRACoL organization known as the G7 method, as an alternative to ISO 12647-2. This approach uses a novel concept of controlling the press calibration based on gray balance through out the tonal range using a neutral print density curve (NPDC) rather than solid ink film and dot area as outlined in ISO. The objective of the paper is to evaluate the different methodologies. This study evaluated the application of the two methods as a practical tool for setting up and controlling a sheet-fed offset press. This was achieved through several controlled press runs using a combination of conventional and UV cured ink sets on different presses. The press trials carried out for this investigation followed the set procedures outline in the ISO12647-2 and G7 documentation. The ink sets used were all ISO compliant. The G7 calibration test target was imbedded in the image printed and was used for all trials as the requirements of this method dictated the use of specialized targets and software. The methodologies were evaluated using four distinct press trials. These consisted of printing using linear plate curves and then adjusting them based on the print conditions and the methodology followed. The results discussed in the paper show that the ease of use of the different methodologies varies. Each of the methodologies have shown different advantages and disadvantages and these area discussed in detail.

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