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From: lauren@vortex.UUCP (Lauren Weinstein)
Newsgroups: net.video
Subject: converting film to video
Message-ID: <299@vortex.UUCP>
Date: Fri, 13-Apr-84 23:38:00 EST
Article-I.D.: vortex.299
Posted: Fri Apr 13 23:38:00 1984
Date-Received: Sun, 15-Apr-84 01:25:22 EST
Organization: Vortex Technology, Los Angeles
Lines: 21

This is still usually done in much the same manner that has been used
since the early days of television.  The "film chains" which do the 
job are essentially just a movie projector with a lower than
normal intensity bulb pointed into a video camera.  There are usually
some mirrors and lenses in between to help with size adjustments and
such, but the basic idea is quite simple.  To avoid flicker between
the 30 frames/sec (NTSC) frame rate and films's 24 frames/sec rate,
the projector (which would usually have a synchronous motor) has a 
special shutter and gearing installed that displays some frames "twice"
rather than the "even" display rate that conventional projector shutters
provide.  This difference cannot be noticed by the viewer but allows
a match between 24 and 30 frames/sec.  

If you try this with an ordinary projector (i.e. by aiming a video
camera at a movie screen) it will work, but there will be flicker
caused by the frame rate mismatch.  For some simple applications, this
might be acceptable.  Be sure NEVER to aim a video camera directly
at a normal projector -- the high intensity lamp might burn out the
vidicon in the camera!

--Lauren--