Film-Tech Forum ARCHIVE: Strange Black "Snow" on One Side of the Frame

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Posted by Patrick Matthews (Member # 2705) on 09-09-2005, 01:44 PM:

I just recieved a print of March of the Penguins and I just previewed it and saw something odd. On the right hand side of the screen there are little black dots that look almost like "snow" that you would see on a TV that is not recieving a signal from a station. This goes from the top to the bottom of the frame and is only on the right hand side of the image. I noticed during build up that the print had quite a bit of oil on it and I have never seen this on any print that I have played. What might be the cause of this? Thanks!

Posted by Dan Lyons (Member # 1454) on 09-09-2005, 02:13 PM:

Maybe a bad pad roller did the damage (tick marks from a burr)? Dirt buildup?

You need to get a new print right away. That film is entirely sky and snow, if you have anything less than a pristine print it will look like hell and everyone in the audience will notice the dirt and damage. [Eek!]

Posted by Patrick Matthews (Member # 2705) on 09-09-2005, 02:15 PM:

I know of the "tick" scratches that you refer to, we had that problem here a few months ago, and that is now what i'm refering to. It's hard to explain but they are smaller than tick scratches would be.

Posted by Olivia Coleman (Member # 3193) on 09-09-2005, 03:30 PM:

We get this problem from time to time from prints shedding and if someone doesn't clean it fast enough the film dust will cook onto the print. This is usually seen on the right side, I think, due to how it ends up sitting on a platter which would be soundtrack up... I'm thinking gravity gets to the better of the dust and it sits more on one side than the other... But that's just a theory!

Posted by Brad Miller (Member # 2) on 09-09-2005, 03:45 PM:

Projectors with a Simplex or RCA type soundhead that have the pressure roller are commonly guilty of this damage.

Clean the print immediately, and I don't just mean one pass or with PTRs. It may be too late.

Posted by Monte L Fullmer (Member # 2797) on 09-09-2005, 03:56 PM:

Look at your pad roller assembly that covers the middle constant speed sprocket - the sprocket that is right after the intermittent (mainly for the Simplex, but other domestic makes as well) assembly that gathers the lower loop of film.

Look at that front (left) roller - the roller that is at the head of the pad arm assembly and the roller that the film touches first. If the front roller has what's called "shoulders" - it's a smaller diametered inner flange that the sprocket teeth passes through between this inner flange and the outer flange of the roller.

What happens is that, if the bottom loop is built too big and I've seen it happen with almost normal sized loops, the film rubs against this inner flange causing these linear scratches, on the base side of the film, to appear.

Order some non-inner flanged ("shouldered") rollers and replace the shouldered ones with these rollers. This will eliminate this linear scratching.

Also, adjust the pad arm assembly to where, with two layers of film over the sprocket, both rollers should still turn freely. If the assembly is closing too tight, this is major cause of linear scratching, since the rollers aren't turning freely, plus major wear on the rollers.

thx-Monte

Posted by Gordon McLeod (Member # 33) on 09-09-2005, 04:30 PM:

Brad said "Projectors with a Simplex or RCA type soundhead that have the pressure roller are commonly guilty of this damage"
They have contact only in the center area so the damage would be there not off to the side?

Posted by Brad Miller (Member # 2) on 09-09-2005, 04:54 PM:

You would think so Gordon, but I've found that the pressure roller will embed dirt into the center of the film (from the left edge of the image over most of the way to the right) and cause a buildup of dirt on either side of the roller (meaning the projected right edge of the image and all over the optical soundtrack). If cleaned immediately, sometimes that dirt on the soundtrack and right edge can be removed. If projected too many times before cleaning, it's permanent.

Posted by Patrick Matthews (Member # 2705) on 09-09-2005, 05:15 PM:

Monte - These are not vertical scratches but tiny little dots.

I'm having a hard time communicating what exactly it looks like, I think. Further examination showed that I needed to get pretty close to the screen to see it and there is no pattern to it. I'm assuming that this happened at the previous theatre it was at as it has never happened in one of our projectors (that is not to say it COULN'T happen). I will clean the print ASAP

Posted by Brad Miller (Member # 2) on 09-09-2005, 05:17 PM:

If the screen was 20 feet wide (you tell us whether you are flat or scope), how far into the image from the right masking do the marks project? That will at least give us an idea.

Posted by Patrick Matthews (Member # 2705) on 09-09-2005, 05:28 PM:

It is 42 feet scope and this film is flat and I would say that it goes in from the right side of the masing 1 foot to 1 and 1/2 feet.

Posted by Brad Miller (Member # 2) on 09-09-2005, 06:56 PM:

Assuming you aren't overly cropping the image, that sounds like pad roller scuffing as Monte detailed above.

Posted by John Pytlak (Member # 331) on 09-09-2005, 09:04 PM:

I agree with Brad and Monte --- likely pad rollers are scuffing the film. Slight roughness or burrs will lightly abrade the film surface, which over a period of time will become visible.

Posted by Gordon McLeod (Member # 33) on 09-09-2005, 09:59 PM:

I have seen some DTS readers also cause a edge scuff as well