Check out this picture as well:

This is the movie "Lagaan Part 2" and is on unspecified film stock. There are no markings on it at all to indicate the stock.

So what could be causing this? Perhaps the platter is trying to wrap the film too tightly? But if that's the case why does it only happen on select prints? And no, this is not happening where the tail is tucked. In fact the tail is never tucked here. BevanPoo's keep the tails secure.

I've seen a ring that is very slightly bent out of round cause inward bulges. Not as large, maybe an inch and a half inward. By the looks of the second picture it seems that the bulge is occuring on the 'side' 90deg from the posts on the ring. Therefore a bent ring would be possible.

This would also explain why it only happens on some prints and on different film stocks.

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I agree that excessive/unever tension during windup could cause this kind of problem. Also, changes in relative humidity (e.g., very dry conditions) could cause excessive curl leading to winding problems.

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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: +1 585 477 5325 Cell: +1 585 781 4036 Fax: +1 585 722 7243
e-mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

You may have an egg shaped center ring also.

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And it's actually on one of my Christie platters...that one doesn't wrap too tight; it winds too soft.

I have seen this occur on many types of platters (Christie, Strong, Speco) and, although it can be caused by too much take up tension, I find that a more likely cause is damaged film.

If it's too much tension it will go away once you fix the platter or move it to another. If it's damaged film it will be there forever, no matter what you do.

The most common cause is roped edges. (Back here, we call it "Spiked".) Somehow, the film has jumped off a sprocket and the teeth have made indentations in the film. Often this is because one of the pad rollers has become maladjusted but it can also occur because of a bad splice. Either, the holes weren't punched in the tape or there may be a misialigned lab splice that wasn't caught in time.

Check the film for "spike marks". Right before the place where they start, I bet you will find said splice. Fail that, it could be a poor threading job or a loose pad roller or intermittent shoe.

Since I know you are pretty conscientious, my bet is on a lab splice. Even though I checked for them religiously I have missed one or two of them in my day.

Once the film is damaged, there isn't a lot that can be done about it. If it's really bad, you MAY have luck rewinding the film back and forth on the bench under high tension. Mind you this is not a good thing to do in every day practice. I can cause scratching and other "not good" things to happen. However, if it's all you can do to save the show, you could try it. The best solution is to get a new print. If you can't do that, there is a chance that the damage will "play out" after several shows. On the other hand, if it's really bad it will cause progressive damage as the film plays.

The telltale is that the film may "buzz" as it plays throught the projector. On occasion, you may find that the film has jumped off the sprocket again even though you have found the cuase and effected a repair. The damaged sprocket holes tend to "lead" the film off-track.

Sometimes, changing the winding orientation (soundtrack up vs. soundtrack down on the platter) will help.

One way around the problem is to use a large take up ring, the Kinoton rings are great for this as they have a locking arm built in and lock solid. That way if the print does bulge the film is nowhere near the module to cause a problem. With the larger diamameter the plate is running slower so the irregular shape is handled better.

The knock on benefit is that its much easier to insert and remove ads and trailers with a larger ring.

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But then again Joe, a Big Bulge will make you very popular.