Computer to plate

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Computer to plate (CTP) is an imaging technology used in modern printing processes. In this technology, an image created in a Desktop Publishing (DTP) computer file 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.

1 Comparison of CTP and CTF
- 1.1 Advantages of CTP
- 1.2 Disadvantages of CTP
2 See also

[edit] Comparison of CTP and CTF

[edit] 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. Plates are produced in less time and more consistently. (Film can move on the plate as it is being placed for exposure, or as it is being exposed). CTP ensures better registration, and image-to-edge repeatability.

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 up to 120 12-inch plates per hour, punched and ready for press.

CTP reduces press 'make-ready' time, i.e., the process of bringing the press, ink and paper system up to a minimum acceptable quality at the beginning of a press run. Reduced make-ready time saves paper and allows the printing of more jobs per day.

The chemistry used to develop the plates is generally more environmentally safe compared to older film chemistry.

[edit] Disadvantages of CTP

CTP requires anywhere from $2,000 upward to $200,000 to implement, depending on the needs of the printer. 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. .

A scanner is required to fully replace the litho camera, in order to handle printing from camera-ready copy, i.e., where a digital file is not available. Unless a very high-resolution scanner is used, the resulting scan may show artefacts (such as stairstepping, or "aliasing") that may be unacceptable.