CTP for Four-Color
A review of the technology today, and a preview of trends for tomorrow
By Danny O. Snow
This article:
* reviews computer-to-plate (CTP) technology;
* discusses its use in four-color printing;
* offers tips on how to get the best results using CTP; and
* previews future developments.
The methods printers use to put words and four-color images on paper have changed dramatically in the past few years. New digital methods have largely replaced traditional processes that involved art boards, cameras and film.
Computer-to-plate (CTP) technology allows the transfer of digital files from computers directly to printing plates. Most CTP systems start with a computer file created in Quark, Pagemaker, InDesign or another format. The file is then output through a Raster Image Processor (RIP) to a printing plate. This process streamlines the traditional printing process, eliminating the need for camera, film and darkroom.
George Whalen, spokesperson for Citiplate, Roslyn Heights, N.Y., notes there are three broad classifications of CTP systems: "thermal" or infrared laser-based systems; "visible light" (red, green or blue) laser-based systems; and ultraviolet laser-based systems. The first two types output to special thermal printing plates; the latter burns traditional UV plates.
CTP equipment makers include Citiplate, Creo, Vancouver, B.C.; Heidelberg, locations worldwide; and Presstek, Hudson, N.H., to name just a few. According to Don DeHart, president of DeHart's Printing Services, Santa Clara, Calif., Heidelberg and Germany-based Karat manufacture four-color Direct Imaging presses that also bypass camera and film.
Digital presses such as the Indigo and Xeikon, says DeHart, use a similar process to the one described above, but rather than imaging a plate, they image a photoreceptor belt or other type of transfer material to bring the image to the paper. In most cases (with the exception of Indigo), a dry ink or toner is used instead of traditional offset inks.
