A machine that generates output for the printing process, using either a film-based paper that is photographed or the actual film for making the printing plates. Input to the machine is typically in PDF or PostScript format, and a laser generates the page image directly on the film.
Today, in lieu of sending work to a commercial print house, laser printers are widely used to create finished output. However, the 2,540 dpi resolution of the imagesetter produces very high-quality photographs and halftones. See CTP
A Brief History of Setting Type
Typesetting dates back to Gutenberg in the 1400s, where lead letters were set by hand and pressed against paper and ink. From the late 1800s into the 1960s, operators of Linotype and other comparable machines keyboarded lines of text that were cast from hot metal into slugs for printing. The metal was reused for the next run. In the 1960s, the "phototypesetter" created film negatives that were used to make offset printing plates. It passed light through a spinning photomask to obtain the font style and then through lenses to create the point size. Subsequently, film was exposed to images on a CRT.
The Chemical-Free Imagesetter
For years, imagesetters have generated output without using the wet chemicals of traditional film. This ColorSpan unit employs a dry process that produces positive or negative film separations. Plates are made directly from the film. (Image courtesy of ColorSpan Corporation.)