G7™ is a specification that defines the factors that can be used to provide consistent gray scale reproduction across multiple devices, processes and media. The main innovation of G7 is the direct measurement of a combined CMY neutral gray scale, instead of separate CMY dot gain (TVI) scales. This allows the well-proven photographic principles of gray balance and exposure control to be applied to CMYK printing, ensuring a close visual match between printed images no matter where or how they are produced.

Although developed initially for commercial offset proofing, G7 has been applied successfully to a wide range of processes including coated and uncoated offset, newsprint, gravure, flexography, dye-sublimation, ink-jet, electro-photography, screen printing and others. By directly controlling the density, contrast and balance of a neutral gray scale, G7 brings the goal of 'printing to the numbers' one step closer to reality.

G7 has enjoyed major adoption in two distinct areas. Firstly, the gray balance and neutral tone scales defined within the G7 Specification have been used as the basis for developing standardized characterization datasets including TR003 and TR005 (SWOP), TR006 (GRACoL) and TR007 (FIRST/Flexo). These and any other printing specifications that are based on G7 exhibit a 'shared appearance' that makes the exchange of image files and proofs between different imaging processes easier and more predictable. See Appendix A for information about developing characterization data sets based on G7.

Secondly, the principles of G7 are also being used to calibrate presses and proofing systems worldwide. The techniques for calibrating a device to the G7 values and principles presented in this specification can be found in the companion document Calibrating, Printing and Proofing to the G7™ Method [G7How-To].

The bottom line: In order to truely reproduce color you must be able to print with good gray balance. If the gray balance changes the color will shift and be impossible to match. Color/shade of paper also has a great impact on color reproduction so as more manufacturers make sheets that are out of G7 specifications color will be more difficult if not impossible to match.