IDEAlliance’s G7 is a calibration method developed to support the GRACoL specification. The “G” refers to calibrating grey values and the “7” refers to the seven primary colors: cyan, magenta, yellow, black, red, green, and blue.
G7 is a press calibration method that uses near neutral as the criterion. An innovation of G7 is that it defines substrate-corrected grey reproduction aim points to achieve a consistent visual grey scale which can be applied to diverse substrates and different printing methods. It defines tonality using Neutral Print Density Curves (NPDC) instead of traditional dot gain (TVI) measurements.
G7 Master Printers are qualified by IDEAlliance based on their ability to print to G7 standards. As of September 2010, there were 512 qualified G7 Master Printers. These companies are concentrated mainly in North America with a smaller but growing number in Asia.
Since G7 contains aim points but lacks associated tolerances, it is not a fully defined specification. In order to advance G7 toward a fully defined specification, this research assessed 85 P2P25x characterization data sets submitted by 85 G7 Master Printers with respect to variations of paper white, process ink and overprint solids, and grey reproduction conformance.
This research studied the G7 method using the GRACoL (2006) data set as a part of the specification. ISO 12647-2 was also used as a reference to help study G7 tolerances.