The Virtual Press: Printing's Future
By Ron Ellis
Standards have begun to have an interesting impact on the printing industry. As print buyers begin to familiarize themselves with standards and specifications such as GRACoL, SWOP and ISO they begin to expect the color that printing to these standards produces. One result of this is that customers have started to expect that printers in different locations should be able to match the same output. For those printers calibrated to these standards and specifications this is not a problem. What has been even more interesting is that in the US, users of specifications such as SWOP and GRACoL have started to require that their vendors match these specifications – even when printing using non-traditional print methods. For example while it may be easy to match SWOP on an offset press many printers who are printing using gravure, flexo, and silk screen are also matching these same specification. A good example would be several large national printers who are printing to SWOP using Flexo. Other examples include wide format and billboard printers who uses GRACoL as an aim for their solvent based products. The use of standards and specifications has given printers and buyers targets. The use of these targets has now spread beyond offset printing.
One interesting byproduct of this movement is something David McDowell, a former Kodak scientist and a US expert to ISO TC130 , calls the virtual press. In an article from March 1999 David McDowell writes about a concept called the reference printing condition. He states, “The reference print condition would be the aim for prepress…The color transforms used, in modifying the data before making the plate for the press, would convert between the reference and the actual press performance.” In David’s early example from the article “Reference Printing Conditions; What Are They & Why They Are Important?” he used the example of the early SWOP specification, and points to examples such as Reader’s Digest and National Geographic. (There are many more examples of this now because of G7 calibration methods, and datasets such as GRACoL and SWOP.) The article also assumes that the reference condition is based on color aims, not density based aims. Now that it is 2009 we have true color based datasets such as GRACoL and SWOP, as well as proven calibration methods. The idea is that a print condition such as GRACoL or SWOP becomes a virtual press. For example, when running a digital press it is easy to simply add a color ICC profile and change the print condition to whatever the profile is describing. On a calibrated digital press this simple change of target ICC profile to GRACoL will make that device emulate a sheetfed-offset press targeting GRACoL. In this case GRACoL has become a virtual press – a print condition emulated on that device. While you can see how it is easy to make a digital device such as a proofer or digital press match another device, other more traditional devices are not far behind.
In the recent past making multiple presses and sites match was a challenging process, difficult to accomplish and almost prohibitively expensive. The ISO TC 130 Working Group (of which David McDowell is a leading us contributor) recently submitted a document titled ISO 10128 Graphic technology — Methods of adjustment of the colour reproduction of a printing system to match a set of characterisation data. This document outlines three methods that can be used to calibrate a printing machine. The first of these methods is performed by matching tone value curves. This method consists of matching ink solids and dot gain. The second method consists of using a method called the near-neutral method, which uses gray balance similar to the G7 method. The third method uses CMYK to CMYK multidimensional transforms, which most commonly would be ICC based color transforms. Along with these methods there many vendors developing software designed to accomplish these tasks. With new software such as IDEALink Curve, Heidelberg ColorToolbox, and Alwan Print Standardizer it is now relatively easy to make even offset presses and other less predictable technology hit desired target conditions. This can be seen with the ease of which many printers use the G7 method to keep their presses aimed at GRACoL. The same G7 method can be used to target other print methods ranging from gravure and flexo to silkscreen to GRACoL as well. While these other print methods will not be as accurate as sheetfed they will bear a common visual appearance. The difference is just how close the output comes to the target data set.
Other new tools such as Alwan Print Standardizer come even closer. This new tool takes readings from jobs that have been scanned using a press scanner such as an Intellitrax, and averages the jobs (discarding out of tolerance jobs) so that the user can easily generate new curves to keep the press aimed at the target. Combine tools like this with closed loop scanning, ink presetting, digital presses, and optimized prepress systems and we have an ability to hit repeatable color that has not been possible until now.
You can imagine that all digital presses in the future will come with a number of standard print conditions that they can match. Currently this is typically SWOP, GRACoL, ISO, and SNAP. Many people have asked how many different data sets would be required to cover the range of print methods. If you were to have different data sets for each print method and stock the number of datasets could be endless. FOGRA already has nearly 50. Some people think it is a simple as one data set, with an aimpoint based on color such GRACoL. Although they would not all hit it perfectly, they would all be aiming at the same target and different processes would be capable of coming closer than others to the target condition. Others believe that as few as five or six would cover the range of print conditions adequately.
Repeatable color has long been a dream in printing. Once the color is repeatable it offers another benefit – the ability to edit or alter the printed result consistently on top of the repeatable condition – and this is a big deal. (I shudder to think of the financial impact of every machine being able to print the same.) Lets face it – compared to some other manufacturing processes printing sometimes seems to be in the stone age – although that craft aspect also has graced it with a certain charm. There are technical benefits to this being able to hit a target. This means when you can print consistently you can also overlay additional conditions on the prints – the virtual press. This could be used to hit an industry standard condition, or it could be used to repeat a match to a custom print condition. It also probably means that as the mystery of controlling color on a printing press goes away buyers will begin to ask for standard aim points and printing specifications. At that point the question will be how close can you get, and is it close enough to meet your customer’s needs.