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, in addition to the offset printing industry, embraced a subset of the PDF format referred to as PDF/X1-a. This industry specific subset is one version of the PDF/X (PDF for eXchange) set of standards.
The following items have each been considered part of prepress at one time or another:
- Typesetting involves the presentation of textual material in graphic form on paper or some other medium. Before the advent of desktop publishing, typesetting of printed material was produced in print shops by compositors or typesetters working by hand, and later with machines.
- Copyediting (also copy-editing) is the work that an editor does to improve the formatting, style, and accuracy of a manuscript. Copy (as a noun) refers to written or typewritten text for typesetting, printing, or publication. Copy-editing is done prior to the work of proofreaders, who handle documents before final publication.
- Markup A markup language is an artificial language using a set of annotations to text that give instructions regarding the structure of text or how it is to be displayed. Markup languages have been in use for centuries, and in recent years have also been used in computer typesetting and word-processing systems.
- Proofreading traditionally means reading a proof copy of a text in order to detect and correct any errors. Modern proofreading often requires reading copy at earlier stages as well.
- Page layout is the part of graphic design that handles the arrangement and style treatment of elements (content) on a page.
- Screening of continuous-tone images such as photographs
- Page assembly or stripping
- Imposition, or the combination of many pages into a single signature form
- Trapping, also known as spreading and choking
- Separation, or specifying images or text to be put on plates applying individual printing media (inks, varnishes, etc.) to a common print.
- Platemaking, the photomechanical exposure and processing of light-sensitive emulsion on a printing plate.
In most modern publishing environments, the tasks related to content generation and refinement are carried out separately from other prepress tasks, and are commonly characterized as part of graphic design. Some companies combine the roles of graphic design and prepress production into desktop publishing.
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), the final product (books, newspapers, product packaging), and 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 an analog one.
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