Slit-scan photography works much like a rolling shutter does—the sensor continually collects image data but the shutter never actually closes, hence its use in determining a "photo finish"—whatever crosses the camera's view first, appears first in the photo set. Or at least that's how its supposed to work.
Slit-scan photography is also really useful for creating psychedelic art where colors flow from a point. You can see examples of it in 2001 during the "stargate" sequence or just about every single time the USS Enterprise stretched as it entered Warp Drive in The Next Generation. But what happens when the latter effect happens during the former event? Our friends at Oobject have assembled 11 examples of these far out photo finishes.
If those photos havent got you questioning physics, check out these images of atoms, universes, and everything between; some movies about moving picture machines, and these camera cars.
Beautiful cycling photo finish with lots of bikes
Note how the backs of the cyclists are sometimes in an exaggerated arc as the vertical movement of them pedaling, over time is captured in a single frame.
Lunging photo finish in cross country skiing
Note the bending of the ski poles due to vertical movement.
Turntable portrait with slit-scan camera iPhone app
You can try this at home.
2001 A Space Odyssey: Unwrapping the Slit Scan sequences
This site shows an attempt to reverse the distorting affects of slit scan images as used in the movie 2001, in order to decipher them. The results are far from conclusive but you can see some things that are less abstract.
The Closest Photo Finish Ever
A cycling Olympic gold medal by a thousandth of a second.
Sample Image from Qualisys PhotoFinish Camera