Practical GRACoL

The holy grail of printing is a visual match from proof-to-press. In a perfect world, the content creator should be able to produce an internal proof that is within 5% of the final print run. This all sounds like a goal only our grandchildren will achieve, but the reality is that with the introduction of new initiatives by IdeAlliance, the introduction of the G7 press calibration process and the GRACoL printing specifications, we just might see this sooner than you think. The truth is, this has been setup in a number of printers within Canada, and more are getting on board.

Here’s the Concept
The presses are calibrated via a method called G7, and plate curves are created with specific goals; colorimetric grey balance at the midtones, image contrast and image weight. Using this system, a visual match is achieved within specific tolerances.

Before starting the G7 calibration method, you need to make sure the device being calibrated, (printing press, proofing system, etc.) is in good working order and operating stably. Like any other calibration method, G7 won’t stabilize an unstable device! An ICC profile is made publicly available and used downstream by the content creators for proofing. This gives the designer a target to aim for and an ICC profile to use in proofing. A connection between creator and printer is made.


The proof:

Sure the concept sounds good, but does it actually work? The answer is, yes, on many fronts. Sina Printing was recently certified as a Master GRACoL Printer. What that means is a qualified consultant conducted an audit of their production workflow, created custom CTP curves targeting the GRACoL specifications and submitted their final press sheets for approval. Once approved, they are listed as a Master Printer and gain respect in the print buying community as a printer that can hit a specific target-GRACoL.

If you are an agency looking to buy printing, it makes sense to look for a printer that has been approved as a GRACoL Master Printer and set up your internal proofing using the GRACoL2006_Coated1v2.icc profile.

Mike Meshkati from Sina Printing says: “Since the G7 calibration and GRACoL setup, we have seen faster make-readies and a significantly closer match to our proof on all our presses.”


The details:

In the past, we have setup presses to target specific dot gains (TVI) and solid ink densities. But, the trouble with this method is that it’s completely different from the more recent colorimetric approach being adopted in colour management. Now that colour management has proven itself, we are able to apply the same concepts to the press.

What we are doing with the G7 calibration method is using grey balance and lab values to ensure that the press is not just matching the numbers, but also matching visually. This is were this system differs from the more traditional approach. When a device is grey balanced, you are establishing a baseline for which all other colours build from. It is not all that different from the days of running a drum scanner. We would set out white point (in this case the paper), then set out black point and lastly, adjust the cast to ensure grey balance. Once those three main variables were locked down, the secondary colours fell in line.

If you want to learn more about the G7 calibration method and the GRACoL specification you can visit www.gracol.com.

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