[Frameworks] Filming a film projection

[Scott Dorsey]

If the speeds are mismatched, they will flicker at the difference rate.

Try it yourself, stick a piece of paper in the gate of the 35mm projector,
or a small groundglass, and look at the image projected where the film would
be.

With a 35mm camera that has a mirror shutter, you can adjust the camera 
speed and shutter phase so that the image in the viewfinder is completely
blank... that is the time when the shutter is closed and the viewfinder is
open comes when the projector shutter is closed.  It can take some juggling
to make everything work out right if you're doing everything wild... 
crystal sync makes this much easier...
--scott