Everything starts with calibration
One common misconception regarding G7 is the assumption calibration can be skipped prior to profiling, because the ICC profile itself should correct for neutral density. While this may be technically true, such an approach can prove problematic, for several reasons.

First, achieving G7 compliance is not the same as maintaining it. With inkjet printing, in particular, G7 calibration is the best basis for process control because, with few exceptions, there is no way to directly adjust colours on the printer. Instead, control over colour reproduction typically resides entirely in the RIP software.

Second, while in most cases the RIP software will rely on an ICC profile, the generation of an optimal ICC profile in the first place is no trivial matter. ICC profiling software from different vendors can produce different results and the selection of parameters can be ambiguous or subjective. Very often, different operators using the same software will generate profiles that produce somewhat different output.

Third, correcting for day-to-day colour drift with frequent reprofiling can become time-consuming and introduce errors and inconsistencies. G7 calibration, on the other hand, is quick, with virtually no parameters to configure, and yields a simple pass/fail outcome.

When an ICC profile is generated for a printer that has already been calibrated to G7 targets, that calibration acts as the foundation for the profile. So, except in some extreme cases, any colour drift can be corrected by simply reiterating the calibration curves, which is fast, requires minimal operator skill and avoids the need for reprofiling.

For sign shop owners, this is one of the most common return-on-investment (ROI) justifications for adopting G7.

Christopher Brown is the manager of Mutoh America’s advanced engineering group (AEG), which develops spectrophotometers, calibration software and other colour management and digital image processing systems for the company’s inkjet printer/cutters. For more information, visit www.mutoh.com and www.idealliance.org.