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This topic comprises 3 pages: 1 2 3
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Author
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Topic: What to do about motorboating prints?
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John Hawkinson
Film God
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Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002
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posted 03-09-2002 11:24 PM
This weekend, we're running all 3 Indiana Jones movies. As you might expect, prints are not in the best condition. But for the most part they're better than can be expected. One annoying problem is that some reels of Raiders of the Lost Ark (Technicolor's only print, bleh) and Indiana Jones and the Last Crusade exhibit motorboating on the right channel. I assume this is due to some sort of failure over time, though the precise failure I don't know what. There are also ocassional visual registration problems, where the corner of the frame becomes visibule in the aperture for seconds at a time. I'm pretty sure that our sound heads are in alignment; buzz track was run recently, though I'll run it again soon to verify, but other prints have been just fine, and the visual registration issues seem to be a sure confirmation of a print problem. So what's the fix? One thought was to try to move the photocell by hand until it sounds "OK". This seems a dangerous plan since the problem goes and comes and it seems conceivable that alginment sufficient to play it would fail to play properly registered soundtracks. I'm loathe to try this. The solution I'm going with is to patch the left premplifier output off our CP65 into the CP65 Mag/Aux center channel, and run the affected portions of the film that way (with the booth monitors listening to the right preamp output to go back to regular Dolby A when the affected portions of the print clear). Is there a better solution? Any good advice for this sort of thing? Oh yeah -- if you book Last Crusade and have any option, don't get it from TES if you can get it from ETS. --jhawk
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Brad Miller
Administrator
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Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99
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posted 03-09-2002 11:37 PM
I don't recommend you doing this as normal practice, but since you have R3s there *is* a way you can cheat your way through this. You should check with your tech first to make sure he won't come attack you later though.Hopefully the lateral guide arm that rests on the top of the sound drum has a round knob. Some of them have a square knob. If you have a round knob, take a piece of masking tape and cut out a tiny arrow out of masking tape and apply it to the edge pointing straight up. If you have a square knob, take a marker and put a dot on one of the 4 sides and make a note of which direction it is pointing (example: pointing at 1:00). Below I have a picture of this done with white Artist's tape for clarity. Now run your print and assuming the tech didn't tighten it down too tightly, slowly rotate it until your motorboating is gone. Don't turn it more than 1/2 rotation. If it doesn't clear up within 1/2 turn, you are going the wrong way. Then just make damned sure you put it back. Also beware you may not be able to get it exactly back to *perfect*, but if your tech doesn't mind running through another A-chain to help you get through these special shows, that should be enough of a rig to solve your problems. Also note that you will probably not have perfect Dolby NR decoding and matrix steering, but with a shrunken print you've got to do whatever you can. No test film can possibly align it.
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John Hawkinson
Film God
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Posts: 2273
From: Cambridge, MA, USA
Registered: Feb 2002
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posted 03-09-2002 11:43 PM
I believe the new print of Raiders is not handled through TES.Thanks for the recommendation, Brad. Indeed, round knobs here. I suppose adjusting the lateral roller is a lot easier than messing with the photocell position. We can certainly redo the A-chain after this, though I am a bit concerned with how the non-shrunken portions of the print will play... --jhawk
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Steve Kraus
Film God
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Posts: 4094
From: Chicago, IL, USA
Registered: May 2000
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posted 03-10-2002 10:08 AM
My personal JJ didn't have a legitimate R-something 70mm SH to go under it so in converting an R3 by-pass was the way to go although that aspect wasn't finished until after I had sold the machine. Mark machined the JJ casting for by-pass as per the Strong blueprint but another fellow turned rollers out of brass stock rather than buy the actual kit.John remarked: >That JJ bypass soultion probably works OK, but I don't like it >because it's kinda an ulgy fix! The rollers outside the SH look just like those on the R8 interlock setup so I'm used to that. What is truly ugly is that black JJ Strong was showing. Does anyone know if that is the standard on new production? (Is there any new production?) Brad admitted: > will know. He knows everything. Wow...we agree on something!
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Steve Guttag
We forgot the crackers Gromit!!!
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Posts: 12814
From: Annapolis, MD
Registered: Dec 1999
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posted 03-10-2002 04:27 PM
The reason? As far as I can tell, economics. The R-3 now works for both JJ and SA operation. No need for two soundheads to be available. The noted film damage did indeed occur on the soundhead (excessive film curl would have the picture area rub the middle of the film). However, I have never found a situation where this couldn't be adjusted out. I am with Brad on this one, I MUCH prefer running the 70mm film through the soundhead rather than around it. Unlike on other 70mm machines (like Norelco or Cinemeccanica) the 70mm film path on the JJ (or even the Simplex PR-3570), the last sprocket moving the film out of the system is in the projector head itself. Each roller in the film path adds some amount of friction. Depending on one's platter placement and strength of the take up, this can cause the film to sag, bounce or even stall on it's way back to the platter. One thing I'm happy to say is that Kelmar supports the R-50 soundhead (and R-20 for you standard drive lovers) so your 70mm film path can properly be routed though the optical soundhead on onto your take-up device (preferably a reel, of course ). You have to order the "JJ" version of the reverse scan reader but it works quite nicely. Steve ------------------ "Old projectionists never die, they just changeover!"
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