Journal ofTaiwan Normal University Humanities & Social Sciences
2004,49(1), ) -28
Dot Reproduction of CTP Plates on Paper
Yung-Cheng Hsieh
Associate Professor in the Deparpment of Graphic Communication Arts, National Taiwan University of Arts.
Abstract
Yu-Ju Wu
graduate student in the Graduate School of Applied Media A口s ，
National Taiwan University of Arts
Computer-to-plate (CTP) is a completely electronic system that produces print- ing plates for direct mounting on the printing press without the use of film. With CTP technology,
text and graphics are digitally transferred directly from the computer to the printing plate,
making the image on the plate a potentially more accurate repro- duction than one done from film. Computer-to-plate reduces the plate-making process to minutes instead ofhours. Compared with the conventional printing method, the CTP technology can save manpower and production time for printers, as well as reduce pollution. The adaptation of、 and investment i n, C TP t echno- logies h as been a major i ssue i n Taiwan's p rinting i ndustry since 1998. The main considerations regarding CTP investment include CTP's production time, cost and dot-reproduction stability and quality. Therefore, the stability of the CTP plates and their quality of tone reproduction are the two major concerns of potential CTP investors.
This experimental study investigated the differences between three major CTP plates and one conventional Pre-sensitized (PS) plate in Taiwan, with regard to dot- reproduction quality, stability, a nd relative c apability 0 n p aper. T he C TP P late materials used in this experiment included S ilver Halide, Photopolymer, Thermal and PS plates. A digital test form and color con- trol bars were designed for the three CTP plates, and a film generalized from the test form and color bars was also developed for exposing the PS plates. Twenty sets of plates were used for each of the four plate types, and their dot images were m easured by G retagMacbeth D 118C. The plate readings were t hen e ntered onto s tatistics s oft- ware f or a nalysis a nd t he best 5 凹的 of plates were s elected f or t he final press runs. One hundred sheets were printed for each set of plates and 50 of them were random1y selected for the final analysis. Therefore, a total of 1000 printed sheets were sampled and read by a Gretag SpectroEye. The dot reproduction attributes of dot gain size, print contrast, and solid ink density were determined statistically.
The results of this study can not only evaluate, for the printing industry, the adaptation of CTP technologies, but also provide a comparison of CTP and conven- tional PS plates with regard to the stability and quality of dot reproduction on paper.
Keywords: Computer to Plate (CTP), Printing Technology, Dot Reproduction Attribute, Solid Ink Density, Print Contrast, Dot Gain.
