Computer-to-plate (CTP) is an imaging technology which helps to transfer a digital image generated in a computer directly to a printing plate. Before CTP, the technology used was computer-to-film (CTF), where the image output was passed to a photographic film, and the output film was then used to make the printing plate. This process is similar to darkroom photography. The CTP technology helps to eliminate all the darkroom processes and hence is cost-effective. CTP is a much faster process compared to film-based printing, so the productivity of printing increases greatly.
CTP technology is based on the construction of the image setter and the source of light exposed to the plate. There are three different construction types:
- Internal drum
- External drum
- Flat-bed image setter
And there are two types of light sources: ultraviolet light lamps and laser diodes. In the case of laser diodes, the energy and wavelength depend upon the type of plates used in the system. It is widely used in the newspaper and magazine printing industry.
CTP has multiple advantages over the other conventional printing processes. The biggest advantage is removing the film generation and chemical usage layer. CTP improves the quality of output as the intermediate films used in other methods can potentially have scratches or other issues. However, there are some disadvantages in the CTP process, the biggest being that the image must always be in the digital format, and if any correction is needed, a completely new plate needs to be created. But overall, CTP is preferred for its faster process and cost-effective nature.