What makes film look like the camera is moving when it isn't?

Master of the Chocolate Martini, Jamie Dunn, asks well, a buttload of questions. One of ‘em is, "Ever watch a movie and the picture wobbles around the screen like someone is moving the camera but it really isn’t moving at all. Whats up with that?"

James, it’s hard to know exactly what phenomenon you’re viewing. Ever since director Leslie Dektor introduced shaky-cam in a series of IBM commercials several years back, half the mediocre directors on the planet seem incapable of keeping their camera steady. Dektor used the technique to suggest angst; his successors mostly don’t appear to have any reason, except maybe to make life for editors miserable.

Assuming that you are not referring to shaky-cam, I suspect you are observing jitter and weave. The terms describe, respectively, vertical and horizontal ‘ride’ as film passes through the gate of a projection or transfer system. In traditional optical projectors, a ‘pull-down’ mechanism actually yanks the sprocketed film through the system, starting and stopping at the precise intervals needed to create the illusion of motion. As film is repeatedly projected in a cinema, wear on the sprockets can cause the film’s path to be deflected in a minor but annoying cycle of ride.

An amusing optical illusion is sometimes created when a film’s titles are superimposed electronically, in television post, rather than optically. The titles will appear to be wobbling, when in fact they are rock solid, and it is the film that is riding. Ok, it’s amusing to me, but I work in TV when I’m not answering questions.

Modern transfer systems don’t use the claw pulldown anymore. The film is advanced by rollers, for more gentle handling. When first implemented, these ‘flying spot scanners’ actually worsened the ride problem, but these days, real-time stabilization has minimized jitter and weave.

I’m guessing that film ride is what you’re talking about, but I’d have to screen something with you to be utterly certain.

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