15th EditionAppendix A: Design and Production—Basic Procedures and Key Terms
The prepress phase includes all the steps that occur between the time the printer receives the typesetter’s files (and any other materials, such as artwork, needed for printing) and the time the publication is put on press, or printed.
Among the first stages of prepress is the creation of blueline proofs, or bluelines, which are photographic prints prepared from film negatives. Through disk-to-film technology, these negatives can now be generated directly from the typesetter’s files. Bluelines are used to examine the layout and position of all elements, including page sequence, before plates are made and the work is printed; they do not, however, represent the quality of the final printing. For works in which the reproduction quality of the illustrations is critical, a publisher may require that the printer supply contact proofs, which can be checked for contrast and quality by the designer and production staff before printing.
Increasingly, printers have eliminated the need for traditional bluelines by using computer-to-plate (CTP) technology. By converting the typesetter’s files to PostScript or PDF, this technology bypasses the photographic phase and allows the pages to be imposed directly onto offset printing plates. Files for works that contain art must have high-resolution scans of the art embedded in them before this conversion takes place. Instead of bluelines, the publisher receives digital proofs, which are generated from the typesetter’s files and checked for completeness and layout but not for reproduction quality.
Another stage of prepress may involve scanning original artwork to produce images for incorporation into the typesetter’s files. With the increasing availability of high-quality scanners and color-calibrated computer monitors, such scanning can theoretically be done at an earlier stage of production by the publisher or even by the author, provided the publisher’s guidelines are followed (see fig. A.9 for an example of such guidelines and chapter 12 for more detailed discussion of illustration preparation). But printers are typically the best prepared to do this kind of work since they have both highly trained personnel and sophisticated scanning devices. These devices outperform most publishers’ desktop scanners, and they can be calibrated to work directly with the printing press and with the type of paper to be used. In-house scanners should, however, be adequate for works to be published electronically, since such publications have different requirements from those of their printed counterparts for image resolution, color, and so forth.