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History of Prepress
During the 1980s and 1990s, computer-aided prepress techniques began to supplant the traditional dark room and light table processes, and by the early 2000s the word prepress became, in some ways, synonymous with digital prepress. Immediately before the mainstream introduction of computers to the process, much of the industry was using large format cameras to make emulsion-based (film) copies of text and images. This film was then assembled (stripping) and used to expose another layer of emulsion on a plate, thus copying images from one emulsion to another. This method is still used; however, as digital prepress technology has become less costly, more efficient and reliable, and as the knowledge and skill required to use the new hardware and especially software have become more widespread within the labor force, digital automation has been introduced to almost every part of the process. Some topics related to digital but not analog prepress include preflighting (verifying the presence, quality and format of each digital component), color management, and RIPping. PDF workflows also became predominant. Vendors of Prepress systems embraced the PDF format, and submitted a subset of PDF as a standard to ANSI and OSI called PDF/X (PDF for eXchange).

Modern Prepress
With the aid of a platesetter, computers can now expose high-resolution (2400+ dpi) raster images of completed impositions directly to plates. A platesetter is similar in principle to a laser printer. Fed with information by a RIP, it uses lasers or thermal diodes to directly expose specific regions of emulsion on a plate, thus transferring images directly from the computer and sidestepping many issues traditionally associated with transferring an image from film to plate. The exposed (and possibly subsequently developed) plate is then mounted in the Printing Press and used to make impressions, or prints. Making plates in this manner is referred to as Computer to plate (CTP). With a CTP system labor is generally saved and the nature of prepress work is altered. Usually this results in a drop in the time and resources required to produce a print job, as well as an enhancement of safety and health (reduction in contact with chemical developers and other toxic substances, as well a decrease in interractions with potentially hazardous machinery and equipment) in the prepress environment. The development of CTP technology has coincided with advances in Information Technology, Material Technology and Laser Technology.

"What you want to be added or left out (of the PDF format) depends on your needs for a specific area or job. On the other side, publishers do want one file that contains everything for any media, and there you have conflict that's not easy to solve."
Roelof Janssen, CEO, Independent System Integrators.
apogee
 
Schematic of PDF workflow at TJ International a book printer No Duff Stuff recommends
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