This is topic bizarre scratches on base side. cause? with photos in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.


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Posted by Dan Lyons (Member # 1454) on 02-22-2007, 03:37 AM:
 
I have encountered a film with the strangest damage to the base; never seen anything like this, or this bad before. It is on 1990 Kodak acetate film stock.

The base side of the film is heavily scuffed, taking on a "frosted" appearance when inspected by hand.
The area of this "frosting" is the entire image area, stopping with a sharp line at the optical sound track which makes me think a sound drum with the texture of sandpaper was involved.

These marks on the base are not typical "cinch marks" either. They go diagonally on screen from upper left to lower right, and give the illusion of black rain or falling dust. They appear with equal intensity on all parts of the projected image.

Aside from pad roller scratching, the emulsion side of the film is in very good shape, exhibiting none of the type of marks seen on the base side.

A sound drum with bad bearings produces vertical cinch marks, what would have caused this damage?





 

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Posted by Brian Guckian (Member # 1678) on 02-22-2007, 07:12 AM:
 
An outside shot this, but it could be where the film came into contact with a guide shoe on a platter roller. Some platter models have guide shoes where the whole width of the film can be contacted - obviously if the threading is done completely wrong. Such errors can also result in the film passing over such shoes at an angle, possibly accounting for the direction of the marks.

The severity of the scratches seem less than say, contact with a platter deck would be, suggesting this indeed happened with a platter guide roller, where tensions tend to be less than in other parts of the film path.

But there are other possibilities, such as the film coming off a roller and rubbing against a support bracket, or even aginst say, the fixed parts of a platter, such as the tree. Stranger things have happened!
 

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Posted by Dave Macaulay (Member # 813) on 02-22-2007, 09:43 AM:
 
Is the redeveloped soundtrack emulsion any thinner than the colour emulsion? These marks look like the "horizontal rain" that Imax prints get after many passes in a dirty environment. The cause is dust/dirt particles abrading the film over many cycles of being rolled onto the platter: ech time they roll up the layers are in almost the exact same spot, and the damage blurs into a short line as platter tension changes cause the layers to match up at different places.
The angle looks like possibly the print ran a long time on a platter where the film is misaligned slightly on takeup so it slides against the pack as it takes up.
 

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Posted by Monte L Fullmer (Member # 2797) on 02-22-2007, 02:27 PM:
 

quote: Dan Lyons

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The base side of the film is heavily scuffed, taking on a "frosted" appearance when inspected by hand.
The area of this "frosting" is the entire image area, stopping with a sharp line at the optical sound track which makes me think a sound drum with the texture of sandpaper was involved

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