8mm Forum: Silent Film Instability at Sound Speed

This is topic Silent Film Instability at Sound Speed in forum 8mm Forum at 8mm Forum.

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Posted by Brad Kimball (Member # 5) on July 27, 2018, 09:44 PM:

Whenever I run a silent print at 24fps on any of my projectors the picture is never free of being shaky yet at 18fps it’s perfect. Why would a silent print with no mag striping be so unstable. I could see if ine edge of the prints had more weight (like a sound print minus a balance stripe). Doesn’t seem to matter which print(s) or which projector. Odd that with 16mm I don’t get the same effect. Only with Super 8 Silent prints.

Posted by Panayotis A. Carayannis (Member # 1220) on July 28, 2018, 03:07 AM:

Are,perhaps,your silents (or,some of them) old and dry copies that need lubrication? And, because the tension at 18 fps is lesser than at 24 they run ok at 18. My guess.

Posted by Steve Klare (Member # 12) on July 28, 2018, 03:07 AM:

-a wild guess:

The only difference I can think of is the stripe.

There has to be a little slop between the perfs and the claw. That means there can also be a little vertical bounce too. Maybe at 24 FPS there's enough added energy in each pulldown that it tends to rattle around before it settles down.

With the stripe in there there's a little added friction and it resists this: kind of like a tiny set of brakes.

16mm doesn't have the stripe, so it has to be immune to this through other means.

I would guess a machine with side pressers in the gate would handle this better than one without.

I usually do 18 FPS with silents: I'll have to give this a shot and see what happens!

Posted by Adrian Winchester (Member # 248) on July 28, 2018, 10:48 PM:

I was going to offer the same theory as Panayotis, as I've sometimes reduced speed to get a seriously unsteady reel through a projector, to avoid unthreading it.

Posted by Brad Kimball (Member # 5) on July 28, 2018, 11:40 PM:

I could see where with a few prints if lubrication of the film was needed it could help, but I must have about 40 different silent prints. Yet with a dry print with striping on it I don’t get any issues. I rarely lubricate film for fear that too much chemical applied over time could be more of a detriment than a benefit. I think I’ve only used my FilmRenew a dozen or so times over a ten year period and only on prints that were utterly disgusting when won on an auction site.

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