Re: Movie shutters vs still cameras

[P3D Marvin Jones <72657.3276@xxxxxxxxxxxxxx>]

> This isn't quite accurate.  Increasing the frame rate of motion picture
> film doesn't necessarily result in less *motion blur*.  While the frame
> rate necessarily limits the *maximum* exposure time (since the film
> is moving it can only be in the gate for so long), even at three times
> the normal 24FPS frame rate, you can still get about 1/80th second
> exposure, which as we know from our still work isn't a particularly
> "fast" shutter speed.  Depending on your degree of pickiness, speeds
> of 1/500th or above are necessary for *really* sharp work if the camera
> is hand-held; you can get away with less if a sturdy tripod is used.
> 
You are forgetting that a motion picture camera does not work in exactly the
same manner as a still camera. For beginners, 24fps does NOT mean that the
exposure is 1/24 of a second; the aperture is closed for about half of that time
as the film repositions for the next frame, so the actual effective exposure is
more like 1/48 of a second. (I think it's really 1/60, but it's been too long
since I was actively involved in film production to remember exactly -- anyway,
you get the idea.) Also, in motion pictures it is extremely uncommon to ever
change the shutter aperture -- changes in exposure are handled entirely by the
f/stop -- so increasing the frame rate does indeed lessen the motion blur by
decreasing the exposure time.

Normally in movies decreasing motion blur is not a good thing. Motion blur aids
in giving the illusion of motion from one frame to the next. When images are too
completely frozen, the result is an unnatural strobing effect. If you're a fan
of Ray Harryhausen, for instance, you can see this in most of his work in which
his table-top animations are moving quickly, like the wings of the harpies in
Jason and the Argonauts. Each individual frame is completely frozen action,
which it would not be if the comparable action were being filmed in real time.
Table-top animators have been working hard in recent years to find ways to
introduce blur into their work by forcing their models to move during a frame's
exposure in order to overcome this strobing effect.


------------------------------