IV. Compare different techniques of typesetting

V. Write a short summary of the following text:

Photocomposition

For the last 20 years, nearly all typesetting was done by photo­composition (also known as filmsetting or photosetting), The advent of desk-top publishing has meant that although the final output is often positive film produced on an imagesetter using photographic techniques, the preparation of the text and illustrations prior to output is much more sophisticated.

Early photocomposition systems copied hot-metal typesetting machines, so that the Monophoto system, for example, consisted of a keyboard identical to the Monotype keyboard, producing a perforated paper spool, which then controlled a filmsetting unit in which the individual characters were glass negatives located in a frame, The instructions in the perforated spool selected the characters, which were exposed onto film one at a time.

This was very slow by modern standards and subsequent photocomposition systems had characters in negative form on a glass disk spinning at high speed, followed by systems using a digitized cathode ray tube. The latest generation of photo­composition output devices produce the image by laser and these are also used to produce the output for desk-top publishing, although the most recent techniques go direct from disk to plate,

Photocomposition systems usually had a separate keyboard unit producing paper tape, magnetic tape or magnetic disk and the coded instructions were used to drive the output device.