Monday, 3 June 2013




by L. J. Spence



Please bear with me for a moment.

A "Geneva drive" is a mechanism that turns a continuously rotating motion into an intermittent rotating motion. A wheel has a pin that catches into a slot made into another wheel - the continuing movement of the pin moves the second wheel around by a certain amount, until the pin comes back out.

The pin will do the same when it catches the next slot and, by equally spacing a number of slots in the second wheel, the two wheels can produce a movement that can be made to turn a required  distance each time. For this reason, a Geneva drive, more commonly named a "Maltese Cross" if the second wheel has four slots, its found in the vast majority of mechanical watches and clocks.

So, what does this have to do with films?

The first Lumiere projectors of 1895 had a claw that caught the film sprockets to keep things in place. However, this would lead to tearing of the film, so very early films could not feasibly be longer than a hundred feet in length.

The British scientific instrument maker, Robert W. Paul, when asked to build copies of film projectors, added a Geneva drive to maintain a constant number of frames per second when film was turning on the attached rollers, but the gentler touch on the film meant that films could be longer - when Paul started making films himself, becoming an important pioneer of filmmaking, he was able to make a version of Dickens' "A Christmas Carol" - "Scrooge, or Marley's Ghost" (1901) that lasted over six minutes!

Put simply, a small mechanism found in nearly all film projectors since meant that what you expect to find in a good film - strong stories, developed and believable characters, and thoughtfully prepared acting - can all be found, if given the time.

This will be why Twitter's new Vine service, providing short videos of up to six seconds at a time, will remain second class to YouTube, but you could have guessed that...


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