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Author
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Topic: Another Odd Scratch
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Pat Moore
Master Film Handler
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Posts: 363
Registered: Mar 2000
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posted 05-09-2001 03:24 PM
Robb;This does sound like something related to the platter more than anything else. Do you run off of all three platters regularly, or mainly off of two disks? Does the scratch show up as pretty continuous, or intermittently with the gaps between the first scratches filled in as the number of runs increases? Are the scratches curved or fairly straight? Initially it sounds like the film is getting abraded on the take-up side of things. I'd check the last roller assembly that feeds film onto the takeup platter very closely. Is one of these rollers particularly hard to reach for any reason? Just some thoughts to start with...
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John Pytlak
Film God
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Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000
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posted 05-09-2001 03:32 PM
Short horizontal or slightly diagonal scratches are usually either "platter scratches" or scratches caused when the film is not being guided properly and rides up on the flange of a guide roller. See the recent thread on "MUT Question" started by Dave Bird a few weeks ago to see how misguiding the film as it winds onto the platter during makeup or takeup can cause the rotating platter to rub across the surface of the print, causing nearly horizontal scratches. Your example of the scratch moving slowly up the image in 6-10 seconds indicates a "roller repeat" that puts the scratches an exact distance apart on the film, usually related to the circumference of the guilty roller. If you can, measure the exact distance between each scratch on the film --- then look for roller(s) having that circumference. It's likely the film was misguided up the flange of one of those rollers, and the roller scratched the print once per revolution. For example, film riding up the edge of a 3-inch diameter roller will have a mark every 3 x Pi = 9.42 inches, and will appear on-screen about twice a second, seeming to move up the image. A burr or rough spot that scratches the film as a 1-inch diameter roller rotates would cause scratches 3.14 inches apart. Let us know what you find. ------------------ 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 Cell: 716-781-4036 Fax: 716-722-7243 E-Mail: john.pytlak@kodak.com Web site: http://www.kodak.com/go/motion
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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 05-09-2001 03:42 PM
Sounds like it could be the final roller on the platter that feeds the film onto the deck is just too low and due to the curl of the film is causing only that portion of the image to scuff on the deck. This assumes you are running soundtrack up. (Another reason not to run it soundtrack down, for then it would be the emulsion side that is getting scratched.) Remember the film should NOT come into contact with the surface of the platter until it is 95% standing straight up. The bottom edge of the film should NOT drag across the surface of the platter deck while it is twisting upright.I have also seen those exact scratches on a Christie projector with too large of a lower loop, but on a Christie they would be emulsion scratches. (Christie now makes slap guards that screw into place under the Ultramittent to prevent this.) I cannot think of anything on a Simplex that would make that mark on the base side of the film. But getting back to the point, those motors on an Alpha platter can be positioned lower to allow for more film clearance away from the platter's surface. The only problem with this is that the positioning is how the platters are actually timed! You could end up throwing prints if you move it very much. In the end, I always drill new mounting holes for the rollers on that kind of platter to protect the film from such marks. Before I forget, take a look at the first reel of the film. Then take a look at the last reel of the film. Do the scratches go away as the movie progresses? If they do, then it is absolutely this last roller. If the scratches are uniform throughout a 2 hour film, then it is something else.
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Paul G. Thompson
The Weenie Man
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Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000
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posted 05-09-2001 10:53 PM
Robb, just seriously eyeball the enitre film path through the platter (starting at the pay-out head) and through the projector and back to the take-up platter. Look for any remnants of angel hair or green emulsion stuff. The right side of the screen would be the non-sound track side of the film. The lower portion of the pay-out fingers of the pay-out head could be causing that. Is the film tracking properly through the fingers and the rest of the pay-out head rollers without climbing or chafing? Since you have discovered the scratch is on the emulsion side, It leads me to this question: What kind of fail-safe/cue detector are you using? I have seen some new style proximity detectors adjusted too close to the film, where the film was actually rubbing on them. If you have those style detectors, look at the detectors themselves and see if you can see a wear pattern on them. (There should be NO wear pattern at all!)
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