Computer to Film (CTF) is a prepress process in which digital print data is transferred to film artwork, which is then used to produce printing plates. CTF was the standard process in the offset printing industry for a long time before it was largely superseded by computer to plate (CTP). Despite the increasing digitisation of printing technology, CTF is still used in certain applications and for special print jobs.
In the CTF process, the digital print data is exposed by a computer directly onto a film, which then serves as a template for the production of the printing plates. The special feature of the CTF process is that the film is used as the medium for exposure, which distinguishes it from direct transfer to a printing plate (CTP). Normally, the film is exposed using a laser, whereby the image is transferred to a light-sensitive layer on the film.
The advantage of CTF was the high resolution and detail accuracy of the image transfer. CTF was able to deliver outstanding image quality, particularly for complex layouts, fine details and shading. Another advantage of the process is its flexibility: film templates can be used for a variety of printing processes and formats, whether offset or screen printing. While CTF has been completely replaced in offset, it is still used in screen printing.
However, due to the intermediate step of film production, CTF is generally more time-consuming and more expensive than CTP. The film has to be produced, developed and then further processed for plate making, which slows down the entire workflow and incurs additional material costs. These disadvantages have led to CTF being increasingly replaced by the more direct, efficient and cost-effective CTP technology.
Today, films are also often printed on transparent films using plotters. Although these have a lower density and are significantly higher in the deviation of horizontal and vertical precision, they are much cheaper and can be produced without any chemicals or exposure technology.
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