G7+: The World’s Best Calibration System Made Better

On the second day of PRINTING United Expo, Don Hutcheson, president of HutchColor LLC, led a lively keynote presentation, titled “G7+: The World’s Best Calibration System, Made Better.”

Hutcheson started the conversation with a series of questions. First, he asked the audience how many of them had heard about G7+. He followed up by asking how many were familiar with G7. Fewer attendees raised their hands when asked if they were G7 experts. Then, there was the last question: How many people actually understood the concept behind G7+.

G7+, Hutcheson explained, is a printer calibration specification that enhances — not replaces —the proven G7 system with new and improved algorithms and benefits.

The Beginnings of G7+

In 2005, the GRACoL 7 project set out to define a GLOBAL reference print condition for commercial offset that could be used equally by all countries — not just the U.S. From GRACoL 7 came GRACoL 7 calibration (or G7). In spite of great resistance, both became de facto standards in the United States and overseas and revolutionized four-color print quality and efficiency, Hutcheson said. G7 has revolutionized the ease, quality, and efficiency of most four-color printing methods, including offset, flexo, toner, and gravure.

G7 succeeded because it just worked, Hutcheson continued. It was “simple, better, faster, easier, and cheaper” than traditional TVI calibration. Today, there are more G7 users worldwide than any other calibration system. Hutcheson said the best estimate he has heard recently suggested 50,000 printers around the globe.

Why Change a Good Thing?

Although G7 was done well, after 18 years, it was time for a refresh. Hutcheson brought up Hippocrates and the Hippocratic Oath, requiring new physicians to swear to uphold ethical standards. The first line is “do no harm,” which became the guiding principle in coming up with G7+.

“We didn’t want it to suddenly change things so much that it was unmet,” Hutcheson said. “We knew if we made G7+ significantly different we’d have a lot of blowback.”

According to Hutcheson, the benefits of G7+ include:

• A more accurate ICC profile accuracy, especially in high-density inkjet printing and richly saturated colors.
• A consistent neutral print density across print production, including low dynamic range systems like textiles, newsprint, and industrial printing.
• Gray balance compliance when SCCA (Substrate-Corrected-Colorimetric Aims) is factored in.

So, what are the differences between G7 and G7+? Hutcheson pointed out several:

• “A completely new tonality algorithm maintains legacy G7 tonality at typical commercial offset (e.g. GRACoL® 2013) ink levels, but improves pictorial appearance on low-contrast media such as textiles, thin papers, absorbent board, etc., with slightly lighter and more natural contrast, especially in flesh tones.”
• “There is virtually no visible difference between G7 and G7+ on typical commercial print production and proofing systems.”
• “G7+ gray balance uses the same CMY triplets as G7 but a more technically sound gray balance algorithm that delivers an improved “shared neutral appearance” and a more visually neutral appearance on strongly colored substrates.”
• “Where SCCA processing may affect gray balance in G7 datasets, G7+ gray balance is completely unaffected by SCCA. This is important when adapting a standard dataset like GRACoL to different substrates.”
• “G7+ verification and QC aims and tolerances, like those required for G7 Master printers are enhanced beyond those of G7.”

Hutcheson went on to show a side-by-side comparison between two images. The top image highlights posterization or “banding” (the kimono and apple) produced by G7 on a high-density inkjet printer. The bottom image shows how G7+ eliminates the posterization.

The top image highlights posterization or “banding” (the kimono and apple) produced by G7 on a high-density inkjet printer. The bottom image shows how G7+ eliminates the posterization.

When it comes to G7+ tonality, Hutcheson offered several takeaways.

G7+ Gray Balance Benefits

• More visually neutral (especially on strongly colored substrates)
• Mimics the ICC Relative Colorimetric intent
• Resists SCAA (Substrate-Corrected Colorimetric Aims)

G7+ SCAA Damage Resistance

• SCAA can damage G7 Grayscale compliance (biased grays, non-neutral 300 CMY)
• SCAA’d datasets need G7 correction (not easy). It limits SCCA value and ease, especially in packaging.
• SCAA and G7+ gray balance use similar math so SCCA has little or no effect on G7+ gray balance.

HDS bonus – Improved Shadow Calibration

• For systems with unstable or uneven three-color shadows
• Web offset on lower-quality paper.
• High-speed inkjet on thin, absorbent paper.
• Fabrics, apparel, and industrial printing.
• By calibrating above 75% on single-ink scales, HDS avoids common three-color overprint problems.
• Little or no effect on good offset printing.
• Can be a user option.

What are you waiting for? Hutcheson asked. New and improved color science? An extra benefit as G7? A similar or better “look” to G7? Future-proof. They’re here. Bringing it back to Hippocrates, Hutcheson said the boat is not rocked, Hippocrates can sleep well.

“G7 was designed for commercial print. G7+ was optimized for a much fuller range of printing technology,” Hutcheson concluded. “That’s the biggest difference.”