Printing

In desktop publishing, text is first prepared on a word processor, and illustrations are prepared using drawing software. Photographs or other art may also be captured electronically using a scanner. The electronic files are next sent to a computer running a page-layout application. Page layout software is the heart of desktop publishing. This software allows the desktop publisher to manipulate text and illustrations on a page.

Depending upon the printing quality desired, the electronic pages may either be printed on a desktop printer, or sent to a printing bureau where the electronic document is loaded onto a high-end computer. If the document is sent to a printing bureau, the scanned images may be replaced with higher-resolution electronic images before printing.

If the document is to be produced in color, the printing bureau will use color separation software to produce four electronic documents, each representing the amount of cyan, magenta, yellow, and black that go on one page. The color separation process produces four full-sized transparent negatives. When these negatives are superposed, they produce an accurate gray-scale negative of the whole page.

Flexible plates are then made from the four negatives, with one ink color per plate. Clear areas on the film end up a solid raised areas on the plate. In this case, all of the color is printed on the paper. Gray areas, which become regions of raised dots on the plate, put down limited amounts of ink on the paper. Black areas produce no raised areas, so the paper remains white. The plates are then attached to four rollers, one for each color. As the paper passes under each of the rollers, it gets a coat of one of the four colors.

Most desktop printers create images by drawing dots on paper. The standard printer resolution is 300 dots per inch, but higher resolutions are available. This is much higher than the computer terminal's resolution of 72 dots per inch.