In August 2010, Disc Makers was approved as a “Certified G7 Print and Proof Provider,” culminating a process that included months of personnel training, upgrades to our printing presses, and calibrations to our presses and monitors.
What will the G7 Certification mean for Disc Makers customers?
It means that Disc Makers’ print shop is conforming to some of the strictest industry standards, that our staff is trained and our equipment maintained to the industry’s best practices, and that ultimately, your print run will be produced to the highest standards possible.
On a practical level, it means that we are better able to match your proof, printed digitally or otherwise. It also means that for reorders or large runs, where a job is run over the course of several days, fluctuations in color will be minimized (or eliminated).
What is G7?
G7 is a calibration and printing methodology created by the IDEAlliance in an effort to standardize the color output for commercial printers. Because of fluctuations in humidity, temperature, ink batches – and a host of other variables – a given print job run on the same press on different days could have noticeable color variations. Compound this with printers in different states across the country and different cities around the world, and a company like Wal-Mart or McDonald’s might see wide fluctuations in the print color on their packages and bags.
By employing G7 calibration, these variations are minimized to the point where, when employed properly, they are virtually undetectable. G7 is currently being applied to many types of printing, including commercial and publication printing, newsprint, and even flexo.
How does the G7 calibration process work?
G7 emphasizes neutral grey balance, in addition to standard ink densities. Neutral grey balance is a critical component of all color reproduction, from presses and printers, to monitors, televisions, scanners, and cameras. Professional photographers, for example, will often include a grey card in an image to use as a reference for color-balancing the shot.
The same principle applies to offset printing: if the neutrals contain a color cast the rest of the colors will invariably be thrown off. That’s the reason obtaining good neutral grays is critical to achieving accurate color on every press run. Unfortunately, dot gain makes it difficult to achieve true neutral balance, especially when the amount of gain varies from ink to ink and across the tonal range of each ink. It’s a complicated situation under the best of conditions.
The first step to G7 calibration is to determine the correct ink densities at which to run the press. This is done by measuring seven primary color patches on a test sheet: cyan, magenta, yellow, black, red (100% M+Y), green (100% C+Y) and blue/purple (100% C+M). There are ISO-standardized Lab color values for these seven colors, so we adjust the ink densities on press until we achieve the correct hues as measured by a spectrodensitometer.
Once the target densities are determined, the primary solid colors are printing to spec, but now the neutrals are out of balance due to dot gain and other factors (in the example below, the entire sheet is significantly red-shifted, most obviously in the skin tones and the three neutral images at the top-center).
The next phase of the G7 calibration is to measure this imbalance, which is done by reading the color values from the test charts into specialized software. This software calculates the difference between how the press is printing the neutrals and how it should be printing them, and provides a lookup table of the required corrections.
These values are then used to apply a curve to the platesetter, reducing the levels of CMYK that are imaged onto the plate to compensate for the dot gain and other imbalances.
By applying these compensation curves to the platesetter, we are removing the inherent-but-consistent variables of the press and taking the burden of compensating for them away from the pressman. When these G7-calibrated jobs are brought up to proper density on press, the primary solids and neutrals should fall into place and bring the rest of the color spectrum along. Since the pressman doesn’t have to fight just to get the color in the ballpark, they can focus on making the minor adjustments necessary to dial in the color and proceed with the press run.
Who is the IDEAlliance?
The IDEAlliance (International Digital Enterprise Alliance) is a not-for-profit membership organization that has been a leader in information technology and publishing since 1966.
Members include agencies, publishers, and printers, among others. The IDEAlliance provides a user-driven, open environment in which members can strategize, innovate, standardize, and implement solutions for eMedia-based publishing.
In addition, IDEAlliance advances core technology to develop standards and best practices for printers and manufacturers across the digital media supply spectrum. Their focus is on the creation, production, management, and delivery of knowledge-based multimedia content – digitally and in print – and G7 is one end-result of their work.
Learn more at www.idealliance.com.