Wavelength (1967) dir. Michael Snow
Wavelength is the vanguard of "structural film" - a movement in the mid-20th Century of simplified filmmaking. Director Michael Snow uses the zoom, the iris, diegetic sound and other techniques, but keeps the camera pointed at the wall on the other side of the room.
We as the audience are not necessarily supposed to invent a story or respond to symbols, although we certainly can if we like. We're simply supposed to enjoy - or at least experience - the minimalist movie. We can look at the zoom in the way we might look at a brush stroke on a non-representational painting.
Although at 45 minutes long, it's a bit much. So in 2003, Snow re-edited the film. He cut it into thirds and overlayed each third on top of each other. It's called Wavelength For Those Who Don't Have The Time.
Wavelength is #336 on the 2012 edition of the TSPDT 1,000 list I’m blogging through. I’ve now seen 451.