PREPRESS: Heat vs. light?

The criterion for choosing between computer to plate (CTP) systems with violet laser diodes and those with thermal laser diodes is anticipated run length. Unlike thermal plates, silver halide plates for violet technology cannot be post-baked for extended life and thus will run to a maximum of about 350,000 impressions. Violet-sensitive photopolymer plates can be post-baked for runs of one million impressions or more, but their resolution is lower than that of silver halide plates.

In terms of print behavior—clean running of the plate, ink/water balance, ink feed, dot gain—and achievable print quality, there is no real difference between violet and thermal technology. Plate throughput and price are also about the same for both processes.