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Re: Subject: RE: Pin Registration (was Re: Kepping)




<< Here! Here!  This is the point. A mechanical pin system must replicate
 exactly what took place in the camera.  And it's often not a question of
 stability, but repeatability, pass to pass.  The physical film dimension is
 set, relative to the perf hole and reference edge, though the actual
 photographed image may be allowed to wander around.  Real-time systems,
 (EPR, MetaSpeed/RTS, JumpFree) know nothing of how the film seated onto the
 registration pins when shot.   >>

I'd like to toss this in for what it's worth:

The dimensional stability of film, when subject to humidity changes, is
actually quite poor.  Consequently, it is altogether improbable that any pin
registration system would ever duplicate exactly what took place in a camera
once a piece of film has been processed, since film inevitably comes out of
processing a different size and "stiffness" than when it went in.  In fact,
unless the telecine and its pin-reg gate live in an environment where
temerature and humidity are very accurately controlled, and the film is given
ample time to acclimate to that environment, it would be most unlikely that
you could pin-reg the same frames on the same machine (without changing
anything) an hour later and come up with the same pixels both times.

There are two purposes pin registration in a telecine gate can serve, both of
which may be important for certain classes of work.  One is to make sure each
frame is positioned in the gate exactly the same way as the frame before it,
thereby keeping all the frames in a clip in perfect alignment by doing away
with any jitter and weave that may exist at the gate; and to place a stepper
"foot" on each frame so the film can't bow or buckle and throw the focus off.

Christopher Bacon
DuArt Video