What is an Imagesetter?

Any printing company has to get the words on the paper. Whether newspapers or book publishers, they often do this with an imagesetter. An imagesetter is the middleman machine. Text must be converted into a form that can be used on a press, and the imagesetter does this job. It is responsible for putting digital text on a piece of film that can be burned onto a plate for the printing press.

The a priori imagesetter is a completely self-contained unit. The operator loads the machine with a film cassette and loads the chemicals, and the machine goes to work. It is controlled by a computer that is usually linked to the pagination computers. When the desk “rolls” the negative, the information is sent directly to the imagesetter, which outputs the image on a negative slightly larger than the page that will be printed.

The film used by an imagesetter is the same as that used in any camera, only in larger sheets. It also goes through the same process. The film is exposed to the text within the machine, then goes through a developer, stop and fixer bath, just as with film in a regular photo camera. The film is then placed on an aluminum or polyester plate, and the image is burned into the plate. The plate goes on the press.

In the days before imagesetters, typesetters assembled long lines of metal type on paper, the type was inked and the image was photographed on a large camera. The metal type process was replaced by computer printers that printed out the material in the desired font. The individual articles or stories were then “pasted up” onto a large sheet of paper the same size as the page and photographed on the large camera. The trouble with these processes is that every time a copy is made, the successive product is of lower quality. The imagesetter solves this problem by putting the text directly on the film.

The computer-to-plate (CTP) method is gaining popularity. This method allows a printing company to burn the plates directly from the pagination computer. The advantage, of course, is that no quality is lost in the conversion from computer to film to plate. Another step is eliminated.

However, many printing companies, particularly newspapers, have older presses that are completely mechanical — with no computerized components. These presses cannot be computerized, so the CTP method will not work. However, the imagesetter still provides a good quality plate that can be used on any press.

Imagesetter operators must be trained to use their particular machine. They must be able to use the computer with the machine and to change the film cassettes and chemicals. They may also be required to do some troubleshooting and maintenance on the imagesetter.

Imagesetters are usually very expensive machines, but not as expensive as CTP machines. Price depends on the size, manufacturer and features. Imagesetters are still a vital part of the printing process.