Computer to plate

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.

CTP methods differ according to the construction type of the imagesetter and the light source used to expose the plate surface.

Because of the setup the laser beam becomes less accurate at the edges of the printing plate and is therefore mainly smaller formats or production with lower quality expectations.

In CTP, the media is registered (held in precise position) in the platesetter during imaging, and does not rely on a separately-aligned pin grid, as is the case with film.