Computer to plate (CTP) is an imaging technology used in modern printing processes. In this technology, an image created in a Desktop Publishing (DTP) application is output directly to a printing plate.
This compares with the older technology, Computer to film (CTF), where the computer file is output onto a photographic film. This film is then used to make a printing plate, in a similar manner to a contact proof in darkroom photography.
Advantages of CTP
CTP has several advantages over conventional platemaking. In CTP, one entire generation (transfer of film image to the printing plate) is removed from the printing process, increasing sharpness and detail. Plates are produced in less time and more consistently, eliminating the possibility of misregistration. CTP ensures better registration, and image-to-edge repeatability than traditional methods. CTP is registered (held in precise position) in the CTP machine itself, and does not rely on a separately-aligned pin grid, as is the case with film. Defects due to dust, scratches or other artifacts are minimized. CTP systems can significantly increase print shop productivity. The fastest platesetters can output more then 300 12-inch plates per hour, punched and ready to hang on the press. CTP decreases dot gain slightly by eliminating the increase in halftone dot size which can occur in the film-to-plate exposure process when negative film is used. (Mainly US) CTP increases dot gain slightly by eliminating the decrease in halftone dot size which can occur in the film-to-plate exposure process when positive film is used. (Mainly Europe) Small portrait presses that typically create 1 or 2 color output can use anything from a standard laser printer, for low quality/low volume, up to a higher-end dedicated platesetter for higher quality and volume.
