Filmless Technology
Computer to plate (CTP)
CTP technology is now firmly established in the world of print. The obvious advantages of this technology make it clear that the “traditional” film-based methods will become progressively less common as time goes by. Even so, as printing presses (and related equipment) do not wear out very quickly, the transition to newer methods has always tended to be quite slow.
In a CTP workflow, digital files are used to make plates instead of generating film as a first stage (fig. 1.8). Because there is no film, image faults caused by foreign objects getting between the film and plate, as well as the expensive and time-wasting revisions they can cause, are a thing of the past. There are also no registration problems caused by “film stretch.” The degradation of dots caused by dot gain (see Chapter 4) is diminished, although not completely, because one of the stages at which the image is physically (rather than digitally) transferred from one medium to another has been removed from the process. Printed images are therefore sharper and registration is better. Environmentally there are benefits, too, because there is no longer a need for the chemicals associated with film processing and manufacture.
Direct imaging (DI)
Direct imaging takes CTP a step further. Not only is film cut out of the process, but the plates themselves are imaged right on the press by an array of lasers. The images thus generated hold ink in just the same way as on conventional offset-litho machines. This means that everything required for the job arrives on-press perfectly positioned—i.e. registered—with no further positioning adjustments required, therefore saving considerable time in getting the job ready to roll. As the main advantage of DI over other methods is this decrease in set-up time, it tends to attract short-run work requiring a fast turnaround.
The best thing about CTP technology is that by removing film from the process, quality is (potentially) increased, and cost and turnaround time are reduced. The best thing about DI technology is that it removes yet another step and sends digital data directly to the press. The next big question, therefore, is whether DI printing will kill off the CTP market in the same way that CTP has almost completely killed off the film market. Again, expect any transition to be slow. CTP is a technology that can be used with conventional presses, and these will continue to have a place on the shop floor for many years to come.
Digital printing
Digital printing presses (fig. 1.9) are much closer to laser printers than they are to the various offset litho printing methods. Instead of conventional ink, they use either toner or a mix of toner suspended in a liquid vehicle. The image that they print is electrostatically generated on a drum rather than on a removable plate, and with each revolution of the drum the image is generated again. This means two things: first, the cost of generating each page tends not to decrease with volume, and second, each time the drum revolves, the image can be changed. Therefore, with digital printing it is possible to generate just one copy of a multiple-page job such as a book. This makes it a very attractive option for the graphic designer who wishes to produce a convincing high-quality proof for a client.
However, do not expect to find digital printing presses sitting next to conventional offset presses. They are an entirely different animal and require their own unique administrative environment. Because the main advantages of digital printing are, for example, individually targeting all the people on a mass-mailing list, or taking on extremely short runs on extremely tight deadlines, it requires a highly optimized internal workflow developed with specific applications such as mailing and fulfillment, e-commerce, and in-house design and photography capabilities. Therefore digital printing presses have a specific customer base that is very different to those who send conventional printing work to conventional printers.