Imagesetter

An imagesetter is an ultra-high resolution large-format computer output device. It exposes rolls or sheets of either photographic film or bromide paper to a laser light source. Once the film or paper is developed, a very high quality black and white image is revealed. Development (processing) usually occurs in a unit separate to the imagesetter, as does raster image processing.
Imagesetter setter output ranges in width; usually between 12 and 44 inches. The resolution of an imagesetter is typically between 1200 and 4800 dpi.
Output on film
The primary purpose of an imagesetter was to produce film, used to expose lithography plates for offset printing. In this function, imagesetters have mostly been replaced by platesetters.
Imagesetter film, however, provides the highest quality exposure for other photo-repro printing processes, such as screen printing for the textile industry.
Imagesetter film is a silver halide-coated plastic film very similar to normal black & white photographic film, except the spectral sensitivity is reduced to a much narrower band around the output of the laser of the individual imagesetter. This allows the film to be handled under a (usually red) safelight, instead of in total darkness like most photographic film.