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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.
Prepress processes The following items have each been considered part of prepress at one time or another: typesetting, copyediting, markup, proofreading, page layout, screening (of continuous-tone images such as photographs), retouching, page assembly (stripping), imposition (combination of many pages into a single signature form), trapping (also referred to as spreading and choking), separation (specifying images or text to be put on plates applying individual printing mediums inks, varnishes, etc. to a common print) and platemaking (photomechanical exposure and processing of light-sensitive emulsion on a printing plate). However, in most modern environments the tasks relating to content generation and refinement are carried out separately from other prepress tasks, and are commonly characterized as being part of a different process (ie: graphic design). The set of procedures used in any particular prepress environment is known as a workflow. Workflows vary, depending on the printing process (e.g. letterpress, offset, digital printing, screen printing), on the final product (books, newspapers, product packaging), and on the implementation of specific prepress technologies. For example, it is not uncommon to use a computer and imagesetter to generate film which is then stripped and used to expose the plate in a vacuum frame; this workflow is hybrid because separation and halftoning are carried out via digital processes while the exposure of the plate is carried out via an analog one. 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. 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 (Available from The Fresh Media Group). 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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