Digital Presses: See How They Run

Digital printing has often been criticized on color management, quality and durability fronts. Reports have circulated that the process tends to drift, can't be color managed or match Pantone colors, and areas of high toner coverage crack during folding. A new technical report from premedia group IPA shows that these criticisms are largely untrue—and that digital printing matches offset and, in many situations, surpasses it in terms of color, print quality and durability.

To dispel the myths surrounding digital printing, the IPA Digital Print Forum conducted a series of experiments comparing output from eight digital presses and a Heidelberg XL105 sheetfed press. Print samples from different digital presses are included in a 46-page Digital Print Forum report, distributed at the IPA Technical Conference last month in Chicago.

The following suppliers and devices participated in the review—Kodak (Nexpress S3000), Konica-Minolta (bizhub PRO C6500), Punch Graphix (Xeikon 6000 and 8000) and Xerox (iGen3). HP did not participate directly, but two users of its devices, North American Color and Cobher Press, provided Indigo print samples.

The comprehensive study covered all aspects of digital print production including color, sheet-to-sheet variability and physical properties such as rub resistance, cracking and fading. The tests also included the assessment of press speed and the ability to match GRACoL on a digital press.

For the first time in North America, deinkability and recyclability of prints from the various digital presses were evaluated. A digital deinking and recycling laboratory was established at Western Michigan University. The results show that digital print material can be deinked, and the paper can be successfully recycled into post-consumer-waste products. (See related story on p.14.)

An interesting outcome of the study was that higher priced digital printing devices do not necessarily output higher print quality—though data processing, speed and postpress features may be more robust on costlier units.

In a test for image consistency, 1,000 sheets were printed and measured. The data shows that there is less than 0.1 density variation in the print processes studied. In another test, the report analyzed the darkest patch and found that the Konica-Minolta device reaches a very dark color with an L* value of six. The ability to match Pantone colors was computed and it was shown that digital and offset presses are able to match 40% to 50% of Pantone colors.

When folding a printed sheet in areas of high coverage, digital prints showed cracking comparable to offset prints. Results of ink scuffing or rub off, which occurs during postpress, shipping and handling (especially on covers), found toner was hardy.

Surface rub resistance showed that most digitally produced samples were better than the offset prints. Only one device showed high susceptibility to rub-off. In separate testing, fade resistance of the samples was evaluated with extended exposure to light sources.

Users of digital printing presses routinely attempt to match output to specified color data. Digital press manufacturers should have a system that can create any desired color on their device—it is important that vendors understand how their toners mix and how to maintain a neutral gray. It is not always necessary that suppliers match GRACoL or SWOP, per se; it is more important that suppliers are able to competently color-manage their systems.

In inkjet proofing, RIP-based systems routinely match press sheet data to less than 2 Delta E. For the digital printing systems, the comparable average Delta E variation ranged from two to six.

Operator expertise and color management processes appear to be a factor in the results. Data in the report suggests that the matching procedure is in its infancy in digital printing.

Suppliers are making huge investments in research and development relating to digital printing hardware, but perhaps are not paying enough attention to software development and integration. The need to color manage a digital press is likely to become more and more important, and the report suggests that suppliers incorporate better mainstream functionality in their digital front end to facilitate cross-media color matching.

So what is the Number 1 digital press? There is no answer. Consider this analogy: It would be impossible to declare the “Number 1 car” in the world. What's most important—gas consumption, safety, horsepower, acceleration? Everyone weighs these parameters differently.

Similarly, it is difficult to declare the Number 1 digital press. But it is possible for you to define the Number 1 digital press for your operation. It is important to gather information so that you can identify the right press for you and begin to ask the right questions, as you understand the challenges and opportunities of digital production printing.

Digital print technology has been advancing steadily over the last decade and now seems poised to achieve expectations such as fast turnaround, variable data and distributed production. Digital printing has come a long way from the color copier business; today these devices are being used in all applications from photo books to transactional printing.

It is exciting to see how digital systems deliver the quality, price and performance expected by the markets they serve.

The IPA Digital Print Forum report is available for purchase at www.ipa.org/digitalprint, at a cost of $99. (IPA members get a discounted price of $49).

Special thanks to Rochester Institute of Technology, Western Michigan University, Ryerson University and Q-Lab for support in testing the sample.