Computer to film (CTF) is a print workflow involving printing of a design file from a
computer
A computer is a machine that can be Computer programming, programmed to automatically Execution (computing), carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic set ...
straight to a
film
A film, also known as a movie or motion picture, is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, emotions, or atmosphere through the use of moving images that are generally, sinc ...
through an imagesetter. Designs are typically created in
desktop publishing
Desktop publishing (DTP) is the creation of documents using dedicated software on a personal ("desktop") computer. It was first used almost exclusively for print publications, but now it also assists in the creation of various forms of online co ...
software packages. An imagesetter is an ultra-high resolution large-format computer output device for CTF.
For multi-coloured printing, the image is broken up into multiple layers representing each of the
spot colors or the
CMYK process colors, this may be split manually by the designer or separated by software in the imagesetter itself. Each color is made into its own piece of film and plate. There can be 12 or more colors used in a single production run; however, 1-6 colors are typical.
From the imagesetter, the film is taken to the plate maker, where the film is laid on top of
photopolymer plate
A photopolymer or light-activated resin is a polymer that changes its properties when exposed to light, often in the ultraviolet or visible spectrum, visible region of the electromagnetic spectrum. These changes are often manifested structurally, ...
material. A vacuum is then drawn to ensure tight contact between the plate and film, the plate is then exposed with
UV light
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of t ...
. The plate is then washed in a solvent solution, typically water, where the unexposed areas wash away leaving a
relief
Relief is a sculpture, sculptural method in which the sculpted pieces remain attached to a solid background of the same material. The term ''wikt:relief, relief'' is from the Latin verb , to raise (). To create a sculpture in relief is to give ...
. It is then dried and given a second and final exposure without the film for durability. The plate can then be fitted onto an
offset,
rotary or
flexographic printing press ready to print the product. A printing plate can produce 100,000 impressions or more before showing signs of wear, after which a new plate can be made from the original film.
With advances in the technology of heat stabilization of
polyester
Polyester is a category of polymers that contain one or two ester linkages in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include some natura ...
film, new-generation
laser printer
Laser printing is an electrostatic digital printing process. It produces high-quality text and graphics (and moderate-quality photographs) by repeatedly passing a laser beam back and forth over a Electric charge, negatively charged cylinder call ...
films provide excellent
image registration
Image registration is the process of transforming different sets of data into one coordinate system. Data may be multiple photographs, data from different sensors, times, depths, or viewpoints. It is used in computer vision, medical imaging, mil ...
and sharpness for multi-colour jobs.
Computer to film is being replaced by the more advanced
computer to plate
Computer-to-plate (CTP) is an imaging technology used in modern printing processes. In this technology, an image created in a desktop publishing (DTP) application is output directly to a printing plate.
This compares with the older technology, ...
(CTP) technology.
References
Printing terminology
Print production
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