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This topic comprises 3 pages: 1 2 3
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Topic: Weird Scratched Prints
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Randy Stankey
Film God
Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99
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posted 06-15-2005 11:44 PM
If they are very light and don't penetrate all the way down to the color layers, black scratches can occur on the emulsion side.
Hold the film up and look at the image. Keep the soundtrack on the right. If the picture is right side up and any words in the picture read correctly, the emulsion side is likely to be the side closest to you. In the projector, correctly threaded film has the emulsion side facing the lamp and the base side facing the screen.
If you are still not sure, you can try the "Lick Test". Lick your thumb and forefinger. Pinch the film between your wet fintertips. (Only on the edge, please!) The side that feels stickier is probably the emulsion.
Vertical scratches usually come from the film dragging across something stationary but they can also come from the film jumping 1/2 way off a roller and riding up on the flange instead of down in the "groove" where it ought to.
In any case, the likely cause is probably operator error. That's why I DEMAND that my projectionists check film at LEAST once per reel. If somebody screws up or if something goes wrong, it will be caught and, hopefully, fixed before it damages the whole print.
The best way to find a place where film is getting scratched is to follow the film path (with your finger) as it runs, checking every roller, bracket and/or keeper that the film passes over or even comes within an inch of. If the film touches ANYTHING it's not supposed to you are probably getting scratched film every time you thread.
If you are getting sever scratching you might even see some colored powdery junk near the place where the film is being damaged.
Finding the place where film is damaged can be tricky because, if it happens on the "home stretch" between the projector and the rewind platter, you won't know the film is scratched until the next show. I got suspended one day because some bastard scratched an entire print on the last run of his shift but it didn't get noticed until I was on duty. I got blamed for HIS fuck up! (Don't worry. The bastard got fired later on! ![[Smile]](smile.gif) )
The best way to find where the damage is coming from is to just "BE the film"! ![[Wink]](wink.gif)
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Randy Stankey
Film God
Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99
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posted 06-16-2005 10:41 AM
quote: Jason Whitlock
Randy, don't you mean keep the soundtrack on the left (not right), with the image facing upright, the emulsion side is closest to you.
That's right. Umm... I mean, correct!
Soundtrack on the left.
That dyslexia thing keeps creeping up on me.
**********
Yes, there is emulsion even when the film is clear. It's just clear emulsion.
A misthread in the gate can cause scratches in the film but, if it was simply misthreaded, I can't imagine how the picture would appear normal on the screen. However, a burr on the aperture plate that hits the film WILL make nice scratches on the film for you.
That scratch that I got busted for happened in a similar way. On the Century projectors I used to work with, the door to the sound head had a glass window in it. People used to simply "slap" the sound head door to shut it. After a while, the wear and tear would start to crack the glass. A little chip of that glass came off the corner of the pane and lodged in one of the failsafe rollers. That piece of glass practically cut the film in half! BUT, if you walked up to the projector and looked at the picture you would see nothing out of the ordinary! Even if you followed the film path with your eyes, you wouldn't see the problem. Only if you got down on your knees with a flashlight and looked at the film going through the failsafe up close would you notice the problem. If you turned the overhead light on during the show (which was a "No-No" because of light pollution) you might be able to see the shavings piling up under the projector. In the dark it would be a long-shot if you noticed it.
Moral of the story... Keep a close eye on your film during the show(s)! Finding the cause of a scratch after the fact can be tricky! Prevention is the best cure.
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John Pytlak
Film God
Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000
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posted 06-16-2005 02:26 PM
quote: Mark J. Marshall
I have two questions about this for Mr. Pytlak (or anyone else who may know)...
1) Is it "easier" to scratch the emulsion or the base? Assuming the film has been playing for a month, and has been regularly film guarded and all that.
2) During pure white scenes - is there any emulsion to scratch? In other words, is an emulsion side scratch during a white scene actually scratching the other side of the base?
1. Either side of the film can be scratched. Measurement of scratching depends on the sharpness and micro-roughness of the point (stylus) doing the scratching and the "loading" (pressure) applied to the film. The back (base) side of Kodak VISION Color Print Film has a scratch resistant polymeric coating that is harder to scratch than plain polyester base. The emulsion side has a clear protective gelatin layer coated on top of the imaging layers, which are in the order magenta-cyan-yellow. Kodak incorporates lubricants on both sides of the film, some of which stays after processing to help protect the film against abrasion. But post-process lubrication will significantly help reduce abrasion, per SMPTE Recommended Practice RP151. As noted, a scratch on either side of the print film will be black, unless it penetrates into the imaging dye layers. An emulsion scratch progresses from black to green to yellow to white as the scratch becomes more severe.
2. Essentially, the density of the image does not affect the amount of emulsion that is on the film. A dark scene has lots of dye formed in each layer. A light scene just has less dye formed in the layers, but all the layers are still there.
Here's a discussion of scratches:
http://www.kodak.com/US/en/motion/support/h1/printingP.shtml#wetgate
quote:
A scratch on the support of a negative film acts as a diffuser that scatters light. Light from the printer passes essentially in straight lines through the undamaged portion of the support and emulsion of the original. When light strikes the scratch, it is scattered and displaced from the straight-line path, reducing the light on the receiving emulsion.
Scratches on the support of a negative film printed onto positive film usually produce more objectionable effects on the screen than scratches on reversal originals printed onto reversal print films. This is because scratches on the support of negative films appear white on the positive film and are generally of lower density than any other white in the picture. In reversal printing, scratches on the support of the original appear black on the screen print and generally tend to blend in better with the picture.
Scratches on the emulsion side of negative films present another situation. Shallow emulsion scratches on a black-and-white negative will appear white on the positive film. Emulsion scratches that penetrate to the support on a black-and-white negative will print black. Scratches on the emulsion side of color negative films may appear colored on the print, depending upon how deep the scratch is and whether image-bearing layers have been disturbed.
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