Film-Tech Forum ARCHIVE: shaky picture - ?

This is topic shaky picture - ? - however... in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Jim Henk (Member # 3628) on 10-08-2013, 02:38 AM:

Century JJ running 35 - gate band pressure dialed all the way clockwise - some cartoons and trailers are mostly steady on the screen, while others still jitter in the gate pretty seriously. Time for a new set of bands, is it?

Posted by Brad Miller (Member # 2) on 10-08-2013, 03:28 AM:

Trap probably isn't aligned. Turret or single lens?

Posted by Louis Bornwasser (Member # 3063) on 10-08-2013, 07:26 AM:

JJ's are especially sensitive to the "gate closure amount". that is the fully closed position of the gate. Does it just "kiss" the bands or does it bottom out squeezing the band tight against the rails that hold the aperture plate?

This is adjusted by the four large screws that hold the gate knob assembly to the mainframe. They are slotted holes and have wandered a bit over the years. They are quite sensitive vertically so be sure to leave them square or you will have focus problems. If they were full forward, you could have the problem you describe.

I am assuming that the alignment of the lateral guide roller to the intermittent sprocket is right, just as Brad mentioned. Louis

Posted by Mark Gulbrandsen (Member # 72) on 10-08-2013, 09:39 AM:

And there IS actually a distance spec for that and it's best set with a gauge block so you can be sure the gate is set absolutely parallel to the trap... I am pretty sure it's in the manual. Louis????

Posted by Leo Enticknap (Member # 534) on 10-08-2013, 10:50 AM:

If some prints look better than others, part of the issue at least could be in the films themselves. Are the wobbly ones mainly older (and therefore slightly shrunk) acetate prints?

Posted by Jim Henk (Member # 3628) on 10-08-2013, 11:10 AM:

Single lens, some stock as recent as a trailer for Midsummer Nights Dream (Kevin Kline version), will have a close look at the manual when I get home tonight, gauge block? Gonna have to look that tool up... Much to examine. Thanks!

Posted by Mark Gulbrandsen (Member # 72) on 10-08-2013, 11:49 AM:

The clearance on the SA was set to .250 for acetate film between the actual bronze casting of the trap and the flat plate the curved runner is screwed to. I do know the JJ is different...

Posted by Louis Bornwasser (Member # 3063) on 10-09-2013, 06:48 AM:

We used a long 1/4 inch allen wrench for the SA.

Posted by Stephen Furley (Member # 1277) on 10-09-2013, 08:30 AM:

quote: Jim Henk
gauge block? Gonna have to look that tool up... Much to examine.

Rectangular blocks of steel ground and lapped very accurately flat, parallel and to size. Several different grades are available and the higher grades are very expensive; the normal 'workshop' grade are affordable, but not cheap. Often known as 'slip gauges'.