Prepress is the term used in the printing and publishing industries for the processes and procedures that occur between the creation of a print layout and the final printing. The prepress procedure includes the manufacture of a printing plate, image carrier or form, ready for mounting on a printing press, as well as the adjustment of images and texts or the creation of a high-quality print file. In today's prepress shop, the form of delivery from the customer is usually electronic, either a PDF or application files created from programs such as Scribus, Adobe InDesign, Adobe Illustrator, or QuarkXPress.
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.
- Copy-editing, is the work that an editor does to improve the formatting, style, and accuracy of a manuscript. Copy-editing is done prior to the work of proofreaders, who handle documents before final publication.
- Markup 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.
- Proofing involves creating an accurate facsimile of the artwork before beginning production runs. This serves as a bond between the printer and their customer that the final product meets an agreed upon standard. Proofs in general can be done for all parts (images, illustrations, texts and colors) of print product. In this part, three types of proofing should be checked and printed out: the print-ready PDF files, the printer's proof and the imposition proof. Print-ready PDF files should be made after the layout using preflight at the printing house. The printer's proof should be printed out in high-resolution and checked by the customer. The imposition proof, which is usually done by the printers, should also be printed out to check and adjust the printing press.
- 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.
- Screening and adjustment of a continuous tone of images such as photographs
- Imposition, or the combination of many pages into a single signature form.
- Separation, or specifying images or text to be put on plates applying individual printing media (inks, varnishes, etc.) to a common print.
- Computer to plate (CTP), or the transfer of the image to the printing plate. A platesetter, or CTP device, uses a laser to burn the image from a computer file onto a printing plate. Plates are made of different materials, depending on the needs of the printing method. Usually rubber, plastic and aluminum are used for plates.
- Manufacturing of a high-quality print (PDF) file, which is used for the final printing.
- Planning, Paper select, choosing a proper paper is also a very important step in prepress.
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 usually called DTP.
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 image-setter 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. That demonstrates that the borders around the prepress are very fluid. Furthermore, – depending on the printing method and the print product – the elements of the prepress of a graphic print production can differ from case to case. This circumstance requires a management of the workflow. It is necessary to manage the responsibility for each part of the workflow. That can mean that employees, who are actually responsible for other parts of the production (e.g. Layout), have to attend to parts of the 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 pre-press. 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 (planning (UK) or 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 pre-press technology has become less cost intensive, 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.
In more recent years, prepress software has been developed which is designed to find as many efficiencies in prepress workflow as possible. These tools are accessed online, and allow different workers to work on one project at the same time, often from different locations. Key functionality automates common steps to reduce errors, reinforce quality standards and speed up production. Examples include automatically re-folioing pages, digital dummies for soft proofs, live linking with Adobe InDesign and pre-flight checking. These tools revolve around a Flatplan and are used in all sorts of prepress including book, magazine and catalog production.
- American Printing History Association — Numerous links to Online Resources and Other Organizations
- History of prepress — Overview of the evolution of digital pre-press from 1984 onwards
- History of Digital Pre-Press Archived 2016-03-04 at the Wayback Machine (last checked on 2008-02-11)
- Press-Ready PDF (PDF/X1-a) — For anyone interested in having their graphic project commercially printed directly from PDF files. (last checked on 2009-03-13)