by Dan Reid

What densities should I use for GRACoL or SWOP printing? I can’t find it listed anywhere on the internet.

Here at RPimaging we frequently get asked what densities to use for the pre-qualification press run before we come on site for G7 calibration. I take a deep breath and sigh when I get these calls. Well it all depends, I respond. That’s not the response they were looking to hear.

Density is a great metric of tracking and controlling fluctuations on a printing press but not a good indicator of how the color correlates to the human eye. Colorimetry is proven to communicate color and provide tolerancing that closely associates with our eyes.

ISO 12647 is the international standard for printing guidance (ISO 12647: Process control for the production of half-tone colour separations, proof and production prints). ISO 12647 is subdivided into different print processes that encompass Offset lithographic, Newsprint, Gravure, Screen and Flexographic printing. ISO 12647-2:2004 for offset lithographic sheet-fed and web printing presses defines CIELAB color coordinates for process color solids, overprints on different press stocks. Clear tolerancing from these recommended aim values is specified in the ISO report.

Determining ideal density values for your press is easy with the Techkon SpectroDens Premium’s ISO Check function. Simply measure a solid process color and the device will report a recommended density adjustment to reduce the Δ E*_ab deviation from the ISO color reference values. We often use this feature to quickly determine the best place to start a G7 calibration press run. You can select different reference ISO paper grades in the Techkon SpectroDens (Grade 1,2,3, 5) and if you will be measuring on a white or black backing (different reference values).

The Techkon SpectroDens Premium’s ISO Check functionality simplifies the complexity of achieving accurate color on press by suggesting the best aim density values for use in production. Simply record the reported density readings as your new production aim values as a starting place for make ready.

— Dan Reid is a color management and G7 Certified Expert at RPimaging, INC.
RPimaging, INC helps clients achieve the benefits of G7 calibration in a matter of days. Learn more about RPimaging, INC services and products at http://www.RPimaging.com