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) 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.
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[edit] Advantages of CTP
CTP has several advantages over conventional platemaking. In CTP, one generation (transfer of film image to the printing plate) is removed from the printing process (eliminating the need for film and it's develop chemicals), increasing sharpness and detail. CTP avoids potential losses in quality that may occur during film processing, including scratches in the film, and variations in the exposure. An imagesetter are usually has an accurate rate of +/-2%.[1] Plates are produced in less time, are more consistent, and at a lower cost. CTP can also improve registration and image-to-edge repeatability over traditional methods.
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. Defects due to dust, scratches or other artifacts are minimized.
CTP systems can significantly increase plate production outputs. Platesetters for newspaper production can output up to 300 12-inch plates per hour @ 1270dpi (dots per inch), whilst for commercial applications a CTP system could output 60 B1 plates @ 2400dpi for higher screen rulings.
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.
[edit] Disadvantages of CTP vs. traditional production
• restricted to digital format- CTP productions require that the basis for the printed matter as well as the imposition, be digital.
• Remaking of plates- if for some reason a CTP plate is damaged, if an error occurs when it's ripped or if something has to be corrected after the plate is exposed, you have to create a completely new, imposed plate.[2]
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