Prepress is the term used in the printing and publishing industries for the processes and procedures that occur between the procurement of a written manuscript and original artwork, and the manufacture of a printing plate, image carrier, or (traditionally) forme, ready for mounting on a printing press.
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.
Recent moves within the Prepress market have meant that many publishers - particularly in the magazine sector - have begun looking at the possibility of handling many of the prepress services within their own companies and facilities. In response, many existing dedicated prepress companies have begun to build and develop "virtual in house production" systems or VIP systems. These allow publishers to take on as much or as little of the prepress process as they desire without the need for extra staff, or expensive hardware and software.
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