G7 printing standard/process provides an efficient method to calibrate a printing press

By Catherine Haynes

The G7 Process

The process looks something like this:

1|Define the goal—What is your definition of gray/neutral? At this point the most common target aims are GRACoL2006 Coated1 or SWOP2006 Coated 3 or Coated 5. Your customers may already be “helping” you out by defining this for you.

2|Run your gray balance target—The most commonly used target is the P2P25. It is small and should fit most print dimensions. Figure 3 shows the P2P25 target.

3|Measure and analyze the target—This was the complicated and time-consuming part of gray balancing a press, where many of us would get stuck and give up. There is now a clearly defined procedure that includes fan graphs to help ease you through the steps to manually calculate your curves; however, if that still sounds too draining, there are also a few different software solutions available, such as Curve3, that make it extremely quick and easy to do. Using the fan graph method or software, you can generate the compensation curves that will assist you in achieving your targeted neutral appearance. Figure 4 shows the recommended curve corrections to gray balance this process to the targeted reference.

4|Apply the curves to the file—This step is really no different then current curve management processes and is typically managed in the RIP.

5|Run the gray balanced plates—This step verifies the accuracy and success of the compensation curves. For processes that have more variability, further curve modifications to fine tune the results may be needed. In all cases, I can not stress enough the importance of sampling. The more samples collected the better you can confirm the consistency of your process, or accommodate for the natural variability of your process. The verification run validates the curves were successful and will pass for G7 Master Qualification.

6|Profile—Depending on your process and the ingredients you have to work with (inks and substrate primarily) you may still need to profile your process and apply color management. In this case different processes will still share a common neutral appearance, but due to ink and substrate impurities and printing characteristics like ink laydown and ink trap, color management must still be employed.

Gray Balance and G7® are two terms that are hardly new to the printing industry. Gray balancing your process is a concept we have accepted for decades as a logical step towards process control and color management, and yet still today it is not widely practiced. In essence, gray balance on press is simply calibrating the printing process similar to what we did for scanners and analog film photography in days past.

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