Digitization of Films for Electronic Pagination - Computer-To-Plate

Digital scanning of existing screened films combined with electronic page assembly is an interesting alternative to manual stripping when output is film and a must for computer-to-plate. However, most scanners are not ideal for this task, because they were developed for other applications. Drum scanners have the required format and resolution, but they are terribly slow for this resolution and format. Most CCD scanners apply an optical zoom system which only yield the required resolution over a small area. Some flatbed laser scanners have the resolution and format but only for reflective copy. However, most scanners are not ideal for this task, because they were developed for other applications. Drum scanners have the required format and resolution, but they are terribly slow for this resolution and format. Most CCD scanners apply an optical zoom system which only yield the required resolution over a small area. Some flatbed laser scanners have the resolution and format but only for reflective copy. Furthermore, scanning of screened material on a digital scanner is not trivial. The digitizing can generate moirewhich has to be eliminated. The threshold must be adapted in order to reproduce the full dot range. Register between color separations can be improved automatically by optical pattern recognition. The scanner must generate low-resolution previews for efficient page assembly. File sizes must be reduced by efficient data compression. Sometimes screen ruling or gradation must be changed using digital descreening.