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Topic: film uneven on takeup platter

Megan Penmann
Film Handler

Posts: 11
From: Gainesville, FL USA
Registered: Nov 1999

posted 04-05-2000 08:40 AM

We've got Strong platters... But like I said before, it's just this print, and it does the same thing on another platter system. Humidity is a possibility. But the air conditioning is broken on that side of the booth, so wouldn't that make the air more humid? (It certainly does feel more humid on that half of the booth). The print is definitely "coning up" as you all describe. I'll check for damage to the film itself when I work next, but when I looked at it before I didn't notice anything right away. We'll see... And maybe I'll be adventurous enough to try winding the film soundtrack down.

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John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999

posted 04-05-2000 08:51 AM

Christie rings are made heavier because they are not "locked" together where the split is. Other rings (like a Xetron) have a latching mechanism to hold the two ends together, increasing it's strength. Christie rings rely only on spring tension to hold them in.

At first I thought that Christie had a better idea, because you didn't need to unlatch anything to release the ring. But it can fall out fairly easily while moving a print. Now that we move prints a lot, I'd rather have the latching kind. I modified two Christie rings to maintain tension for when prints are moved.

I've had two break over the years, but when I looked at the break, it looked as if the casting was made wrong. They wouldn't replace them, even though they agreed it was manufactured wrong because the rings were several years old.

And don't replace those two nylon pins on the Christie ring with steel pins if they break. I did that, thinking I'll never have to fix those again. A week later, someone removed the ring by picking up only one side and bent/distorted the hole on the deck.

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 04-05-2000 09:35 AM

In my experience (on SPECO platters) if a print cones up (we call it "beehive") it's because the guide rods on the yo-yo/take-up control were dirty. If they get crummy, little "rings" of dirt build up and the yo-yo won't slide evenly. This causes the take-up platter to run at slightly erratic speeds.

Also, check that stupid adjustable caster/roller on the take-up. If it's slightly out of line it can cause a bit of beehiving too.

Since it doesn't happen on just one platter, I'd say people are right in suspecting something wrong with the film. My first guess, again, is sprocket damage. ("Spiked film") We used to have that a lot. We buckled down a lot at TT-17 and it's truely a rare occurence, now. Fire a couple of guys and that kind of stuff will STOP. (Or if you REALLY want to hurt a guy, demote him/her to USHER! :O )

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 04-05-2000 01:08 PM

Megan:

Do get one of the Radio Shack or Edmund Scientific digital humidity gauges. If your air conditioning is "broken on that side of the booth", the humidity is probably too high (if the air conditioning is not removing moisture) or too low (if the room is getting hot). In either case, the film curl may be affected adversely. Remember, 50-60 percent RH is best for projection rooms.

Does the uneven wind affect all the reels, or is only one reel affected?

In addition to the "spocketing" or "run off" damage other posters have mentioned, is there any chance the print was "stretched" by abnormally high tension at some time? Excessive tension can deform the film enough so it won't wind evenly.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 04-05-2000 03:31 PM

Check to see if there isn't a roller out of line somewhere (probably in the takeup path). This can cause the stretching John mentioned above. It won't necessarily be far enough off to scratch the film, but it can stretch one side. Does the film lay flat between the projector and platter as it is running?

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Chris Erwin
Expert Film Handler

Posts: 195
From: Olive Hill,KY
Registered: Oct 1999

posted 04-05-2000 07:12 PM

Stop me if I'm totally off-the-wall,but has anybody had leveling problems of the platter itself causing a wind problem?

--Chris

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Megan Penmann
Film Handler

Posts: 11
From: Gainesville, FL USA
Registered: Nov 1999

posted 04-11-2000 10:53 PM

I inspected the film (or so I thought) and found no visible trace of any film damage. So I thought it was a humidity problem from the broken air conditioner. Today we got the air fixed, and the print sill sat uneven on the platter. So I inspected the film more closely and noticed a very small amount of sprocketing on the inboard side of the film. It's so slight that I could only tell by touching the film; the sprocketing is not really visible. Then I checked the projector where the unevenness originated and noticed that a pad roller was too tight. Thanks for everyone's suggestions!

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 04-12-2000 12:56 PM

Megan:

To give an example of why even "a very small amount of sprocketing" on one edge of the film may cause uneven winding and dishing: Print film is approximately 0.0053 inches thick. If the thickness of the film pack on the platter is 12 inches, there are 12 / 0.0053 = 2264 convolutions of film stacked on top of each other in the roll. If the film has sprocket damage along one edge, the height of each perturbation in the surface is magnified by 2264! So if the sprocket teeth nicked the film surface by only 0.0001 inch, the film pack would be 2264 X 0.0001 = 0.2264 inches thicker on the damaged edge. That kind of thickness difference would cause the roll to "cone" or "dish" as it is wound.

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