Film-Tech Forum ARCHIVE: Infuriating scratches.

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Posted by James Waite (Member # 4536) on 11-24-2008, 08:25 PM:

This is my first post so please be gentle. I looked through older threads but didn't see anything that helped me. I've been having the most infuriating problem with scratching prints and I thought maybe someone on here can offer some wisdom.

I've been getting vertical scratches on films. Usually 1 about 25% of the screen width in from the left side and sometimes one in the center, sometimes there's a set of two very close together. The scratches always seem to be in the same place, especially the one on the left.
The problem with my issue is it's erratic, every time I think I have figured out what's causing it there's some indicator that's not the issue.

I've checked everything I can think of as far as advice seen on other threads such as looking for non-rotating rollers.

here's some of the reasons I'm so frustrated.

It only seems to happen on scope.

I'm pretty sure it's in the projector as the first run doesn't usually have scratches, however a couple times it seemed to. We are a second run theatre so they may come in scratched. It always seems to be in the same place though.

Not every film scratches, we played Dark Knight for about 2 weeks before any scratches showed up.
The scratches usually go away before the end of the film.

I've tried running loops and I can't get it to make scratches!? But if scratches don't show on the first showing that implies it isn't the platter.

They are dark scratches do it's the base side.

I had the soundhead redone a few months ago to fix an even worse scratching problem. I have a Simplex projector and the 'felt' pad that holds the film onto the sound drum had worn down enough to let the film slide over the sound drum. It's been replaced and the assembly was realigned. The scratches seemed to go away for a while.

So a couple questions.

I've noticed the teeth on the intermittent are getting really sharp which implies it's getting worn. Could that have something to do with it? Is there something in the gate precise enough to be thrown off by some wear on the intermittent? I've looked at it and I can't see the film touching anywhere in the gate.

If the scratches happen the first time through one of the places it could be happening is the DTS reader. Is there anything in there? I've noticed the main roller seems to stop a little abrupt when spun so it could be dragging but even then the film shouldn't be touching the roller?!

I should stop before I write a book here. Any help or questions please let me know.

Posted by Jeremy Weigel (Member # 4208) on 11-24-2008, 08:43 PM:

Posted by Monte L Fullmer (Member # 2797) on 11-24-2008, 11:30 PM:

Welcome to the Forums!

Sounds like you have a Simple booth then. What is the make of the platters ...also STRONG, or something else?

For scratching could be coming from the platter as well (unless you have a reel setup..)

thx-Monte

Posted by Mike Blakesley (Member # 26) on 11-25-2008, 12:08 AM:

Well...unless a roller is not spinning in the DTS reader it's not in that. The main roller is light enough that it doesn't spin too long. (At least it was on the reader we had.) And the intermittent sprocket being worn won't cause vertical scratches - but it will cause sprocket hole damage eventually. You should get that sprocket replaced.

But back to the scratches - If they are steady scratches that don't move around on the picture, they must be caused by the film dragging over something, be it a stuck roller, a piece of debris caught somewhere, or maybe even a mis-thread wrapping the film around something it's not supposed to go around.

Do you do all the threading? If not, check on everyone's threading practices. You might find your problem.

Posted by Demetris Thoupis (Member # 833) on 11-25-2008, 12:20 AM:

Are you using spools or platter? Are your rollers rolling in the path from the platter to the projector and vice versa? Is your film laying nicely on the rollers and not "scrubbing" itself along the sides of your rollers? Do your platter rollers spin and does your film lay nicely on those rollers and not scrubbing itself along the sides of your rollers? Which side you thread the emulsion on your rollers?
Demetris

Posted by James Waite (Member # 4536) on 11-25-2008, 12:25 AM:

I have a Simplex projector and a Potts platter. single screen, all manual.

I just spent about an hour running a brand-new trailer through from the platter multiple times. I figured since test loops in the projector didn't make a scratch maybe it was the platter.

Again I couldn't get it to scratch. trailer still looked brand new.

I have two projectionists, both of which have been here longer than the problem so I didn't think it could be either of them but maybe I should double check. Normally if they are here I'm not.

stupid question #1. I've noticed the stuck roller comes up as a possibility often on the scratch threads. however, if the center of the roller is indented so that only the edges of the film touch it how could it scratch even if the roller isn't turning? I would think it would only increase tension by adding friction.

stupid question #2 I can't remember if the small rollers that hold the film onto the sprockets (pad rollers?) are supposed to turn or not? Some of them are and some aren't, and again they have indented centers so how could it matter?

Posted by Joe Redifer (Member # 3) on 11-25-2008, 01:43 AM:

Look for flat spots on the rollers (areas that are worn) on all of the platter rollers. Spin them all around by hand to look at 100% of the surface area of each and every roller. One of them might have a small flat spot.

Posted by Brad Miller (Member # 2) on 11-25-2008, 04:09 AM:

Do the scratches move side to side, or are they perfectly steady?

This ONLY happens in scope? Are you positive? Better look at your aperture plate for scope if that is indeed the case.

Do note often scratching is occuring on every pass, it is just that it is so light you don't notice it until the film has been passed through the projector enough times to start to form a project-able line on screen.

Posted by John Hawkinson (Member # 1135) on 11-25-2008, 03:21 PM:

Hi, James.

Best of luck, I'm sure we'll help you get to the bottom of it!

Are you sure its the base side? Check the physical film. Even emulsion-side scratches can be black.

Can you post an picture of a scratched frame? It might give us some clues.

To address some of your direct questions:

stuck roller
Usually a stuck roller won't scratch the picture area, as you note, but it can definitely do a number on the SDDS area and sometimes Dolby Digital. Also, it can cause the film to try to move side-to-side in funny ways (from the increased drag or friction)

pad rollers
Pad rollers are supposed to spin at a particular thickness, and it depends on how they are set. If they're set for two film thicknesses, then they won't spin most of the time. What's important is that they spin when the film rubs against them, and that they don't drag against the film, scratching it somewhere.

Also, flat spots and burrs on rollers can build up when they don't spin, and that can result in scratches if they touch somewhere that they should not.

I would try to get in the habit of watching the print the first time it runs, to evaluate it for scratches, and having your fellow projectionists do the same.

--jhawk

Posted by Tony Bandiera Jr (Member # 2365) on 11-26-2008, 11:15 PM:

quote:
I have a Simplex projector and a Potts platter. single screen, all manual.

I'll bet someone accidently threaded over that blasted lock pin on the takeup slide trolley.

Don't ask how I know this.. [Roll Eyes]

Posted by James Waite (Member # 4536) on 11-27-2008, 12:54 AM:

Thanks for the replies.
The scratches vibrate a slight amount but don't move side to side more than that. I've checked on the film and the scratches are on the base side. We only play two shows a night, usually a different film for early and late show so 75% of the films screened here only play 7 times per week. Whatever causes the scratch is bad enough to do it all in one run. Since the projectionist only has one screen we always watch any film it's first time through in case of bad splices etc. Most of the films (possibly all if some films have come in scratched) have gone through fine the first time.

The thing that's really annoying is I should be able to fix this. Despite how it probably sounds I've actually been a projectionist for about 15 years and actually had a licence back in the days they were required around here.

I know the scratch must be being caused by something touching the film where it isn't supposed to but can't figure out where?! There's so many contradictory indicators. It seems to happen only to scope which implies the apurture plate, however I looked very carefully and there's a couple mms of clearance between the film and the plate. It could be just that the scratches are more apparent on scope becuase of the doubling effect of the anamorphic. I think Nick and Norah developed scratches and it was flat.

The fact that it seems to happen so easy yet I can't recreate it baffles me.

I just about went crazy last Friday when we started Eagle Eye, the first show through had awful scratches in about the places we get them. I was looking at every roller etc to figure out what was causing it. I finally realized if I shone the flashlight at the right angle I could see the scratches on the moving film. I traced them back and they were on the film as it went into the control plate so it must have come in that way and the positioning was a coincience. The print had a lot of damage and splices and green scratchs so it had been through the wringer somewhere.

I asked Paramount to send a new print which I received Tuesday. I put it together myself and very carefully looked to see if it had any pre-exsiting damage. I watched it when it ran through Tuesday night and the print looked flawless.
With many butterflies in my stomach I started the Wednesday night show and was relieved to see there were no scratches.

The indicators I'm getting now is it's either some sort of combination of factors that I haven't been able to replicate or somehow one of my projectionists has managed to learn to misthread in a way that's subtle enough I haven't noticed but bad enough to cause these scratches. I'm going to go over thier threading very carefully the next few times they work.

A new variation has revealed itself. Pineapple Express ran through fine on Friday. The next time I was there to see it was Tuesday. My staff said it had scratched over the weekend so I expected to see the usual. I got something I haven't seen before. There were several light scratches along the width of the film however each scratch seemed to be in 4 pieces from top to bottom with fairly unscratched area between them. The scratches formed bands that roughly lined up with the sprocket holes. My first thought was a intermittent loop was too big and had scraped against something. I ran some test loops through and tried various loop sizes but I couldn't recreate the same pattern even when the loop was way too big and obviously hitting the lower wall.

If anyone has any suggestions I'd love to hear them.

p.s. Sorry for writing another book length post.

Posted by Chris Slycord (Member # 4239) on 11-27-2008, 01:06 AM:

quote: James Waite
There were several light scratches along the width of the film however each scratch seemed to be in 4 pieces from top to bottom with fairly unscratched area between them. The scratches formed bands that roughly lined up with the sprocket holes. My first thought was a intermittent loop was too big and had scraped against something. I ran some test loops through and tried various loop sizes but I couldn't recreate the same pattern even when the loop was way too big and obviously hitting the lower wall.

Are you meaning the scratches were like if the line went straight from one sprocket hole directly across the image to the same one on the other side of the screen (as in a horizontal cut as it appears on screen)?

If so, that could easily be a roller being out of alignment with the platter and just by normal wear some parts get scratched more than others (and so some parts appear unscratched simply because you can't see the light scratch). Or it could be if your deck is slightly warped on one side you end up with periodic scratching because part of the takeup deck rides up to hit the print.

Posted by Monte L Fullmer (Member # 2797) on 11-27-2008, 04:28 AM:

quote: Tony Bandiera Jr
I'll bet someone accidently threaded over that blasted lock pin on the takeup slide trolley.

Don't ask how I know this..

I'll stand up and say that I've done that as well - tagged a print over that damned pin a few times.

But, not as bad when you have an AW3 and drop that roller traveller past the lowest stop pin on the slide rail when rewinding to the bottom platter....that does some pretty nasty scratching there..

Posted by Louis Bornwasser (Member # 3063) on 11-27-2008, 06:37 AM:

I'm with Tony and Monte on this one; the pin on the platter takeup.

Make a loop out of a new unwanted trailer. Thread the entire projector and as much of the platter as you can. Be sure to include the "trolley." Run for 10 minutes. Probably all is well. Now deliberately hook the film around the "blasted pin" and see if you can create the same mark. Louis

Posted by James Waite (Member # 4536) on 11-30-2008, 08:00 PM:

I think I figured it out.

We started Body of Lies on Friday and I was watching the film as it went through the projector. It was threaded by one of my projectionists (Stef) as she was the official projectionist that night.

I noticed I could see scratches from time to time on the film as it came out of the projector and traced them back.

It turns out it was a roller but what I would consider a peculiar situation. The pad roller on the motorized sprocket above the 'shock absorber' loop in the soundhead seems to be the culprit. Since that loop has no defined size we all make it different sizes. Stef had made her loop larger and as the film came out of that roller it was bending slightly for some reason and tocuhing the pad roller which wasn't turning. I could see crap building up where it was touching.
This explains the erractic nature of the scratch and why I couldn't reproduce it. I tend to make my loop smaller so it was never at the right angle to hit the roller. Also a splice could reset it. I had kinda looked at the same place a few minutes ealier and didn't see anything but when a splice went through it started hitting again.

I'm not quite sure why the film was bending. I think the roller is probably stuck a little off center and pushing on one side.

For now we are threading up with only a small loop in that place and as far as I know it stopped the scratches.

On Friday I stopped the film for a couple seconds to make the loop smaller once I realized that was the problem. I watched the film for a bit after the same scene on Saturday and didn't see any scratchs.

I'll figure out what's wrong with the roller on Monday and hopefully everything will go back to normal.

Thanks for your help.

Posted by Monte L Fullmer (Member # 2797) on 11-30-2008, 08:15 PM:

quote: James Waite
Since that loop has no defined size we all make it different sizes

Okey, I can also see what's happening: You have a 5star head with that "shock absorber" roller to the left of the holdback sprocket.

There is actually a defined size that is required for this soundhead: the film needs to be pulled full tight across the holdback sprocket where the 'shock absorber' roller (called a 'snubbing' roller) is fully pulled forward. Then, you back the film over the sprocket one sprockethole, then close the pad roller over that sprocket.

This will still allow the 'shocking' action of the snub roller, but keeps the film tight enough to not allow any slack of the film during startup and operation.

-Monte

Posted by Steve Guttag (Member # 268) on 11-30-2008, 10:22 PM:

Yes, most make the isolation loop too large. It need not be large at all...it should look like a ")" and that is it. It isolates the film from the outside world...which with a platter, isn't going to be too much other than what the take-up elevator might inject.

However, it is a good idea to change the pad roller anyway. The flanges are likely chamfered now. MNR-221s are good though a better roller to use is the SOR4-22 as it is precision ground metal and the inside flanges are under-cut slightly to prevent scratching.

Steve

[ 12-01-2008, 05:50 AM: Message edited by: Steve Guttag ]

Posted by Eric Robinson (Member # 2966) on 12-01-2008, 09:34 AM:

It also sounds like the pad roller arm closing distance may be off since the film can skip sprocket teeth when a splice goes through. If you do work on the pad roller arm, you need to make a few adjustments. Be aware that one of the pad roller shafts is eccentric where it mounts to the pad roller arm. If you loosen the locking screw which holds the pad roller shafts you will notice that one of the pad roller arm shafts does change its relative position with respect to the sprocket when rotated and the other does not.

Note: First replace your pad rollers and ensure that they spin freely on the pad roller arm shafts.

Pad roller arm adjustment steps:

1) Wrap two pieces of film around the sprocket. Hold onto the ends of the film so that they are wrapping tightly around the sprocket. (in the same position they would be in during normal film play)
2) Rotate the eccentric pad roller farthest away from sprocket.
3) Close the pad roller.
4) Turn the non-eccentric pad roller by hand.
5) Adjust the pad roller arm closing distance stop screw so that the non-eccentric pad roller gives a very slight resistance.
6) Remove the two pieces of film and put in one piece of film.
7) Turn the non-eccentric pad roller by hand.
8) The pad roller should turn freely with no resistance.
Repeat steps 5 through 8 until you get the proper result.
Then, adjust the eccentric pad roller distance to the sprocket so that it has the same behavior with one and two film thicknesses.

Posted by Monte L Fullmer (Member # 2797) on 12-01-2008, 01:40 PM:

quote: Eric Robinson
Wrap two pieces of film around the sprocket.

...but, folding a length of film over the sprocket, then close the pad roller over this fold to make the two layers is tons easier to do .... [Big Grin]

But, one needs to adjust the entire pad roller arm assembly first with the stop screw to get the two film thickness with the rear pad roller since that roller is not on a eccentric shaft as the front shaft is.

Then, after the rear adjustment is made, then one does the front eccentric adjustment for the two film thickness between sprocket and roller..if you want to make it an offical adjustment for the record books.

,,and this goes for all pad roller assemblies on a Simplex .. and practically with all two pad roller arm projectors..

-Monte

Posted by Eric Robinson (Member # 2966) on 12-01-2008, 02:04 PM:

quote: Monte L Fullmer
...but, folding a length of film over the sprocket, then close the pad roller over this fold to make the two layers is tons easier to do ....

These techniques are hard to explain in writing, for example, I don't understand what you are saying above.

Nonetheless the information has been made available and the reader could certainly gain from it and he/she could ask for clarification if needed.

[beer]

Posted by Monte L Fullmer (Member # 2797) on 12-01-2008, 02:56 PM:

quote: Eric Robinson
for example, I don't understand what you are saying above.

We old school techs know this one since we were raised with this procedure..but sorry, didn't know I confused you.

To make it simple then:
1-Take a piece of film and fold it in half.
2-Lay it across the sprocket with the teeth coming through.
3-Hold the fold down over the sprocket and close the pad roller over this folded film and the pad roller should still spin freely.

Try this one out for size. - Monte