Film-Tech Forum ARCHIVE: Can't Find Cause of Horizontal Scratch

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Posted by Jacob Szewczyk (Member # 2513) on 01-16-2005, 07:09 PM:

We recently had a weird problem which I and the other projectionists at my theater haven't seen before. We had horizontal scratches across one of our movies. The scratches, from what I could see, did not go all the way across the screen, they were off on the left half of the screen. According to my manager, this use to happen when they used tooth brushes to clean the gears, which we do not do anymore. What could cause this? We use CFS Super Platters and Monee gearboxs.

Thanks alot for any help.

Posted by Brad Miller (Member # 2) on 01-16-2005, 07:35 PM:

Ok, first off tooth brushes on gears couldn't possibly create a scratch on a print any more than wiping your butt after you use the bathroom.

Now let's get to your problem. We need a few questions answered.

First, are you running soundtrack up or down on the platter?

Can you verify if the scratches are exactly horizontal, or are they just a little bit diagonal?

Are the scratches on the emulsion side or the base side? (The emulsion side of the film would be the side facing the lamphouse, and the base side of the film would be the side facing the screen as it is running through the projector.)

Let us know.

Posted by Steve Kraus (Member # 476) on 01-16-2005, 08:22 PM:

He's probably means sprockets when he says gears.

Posted by Brad Miller (Member # 2) on 01-16-2005, 08:29 PM:

No matter. Same answer.

Posted by Jacob Szewczyk (Member # 2513) on 01-16-2005, 08:31 PM:

We are running soundtrack down and they are base side scratches. They looked like they were exactly horizontal to me. Also, I guess what happened with the tooth brushes were every once and a while a bristle ended up on a gear or something that the film ran over and ended up scratching it (thats what my manager said, I never used tooth brushes so I don't know if a bristle would fall off and cause that).

Posted by Brad Miller (Member # 2) on 01-16-2005, 08:41 PM:

First off soundtrack down is evil and is most likely the cause of your problem.

Are you SURE that the scratches are on the BASE side??? I'll bet just about anything that they are actually first degree black EMULSION side scratches. (Hot tip -- just because a scratch is black does NOT mean it can't be on either side.)

Posted by Jacob Szewczyk (Member # 2513) on 01-16-2005, 08:48 PM:

I'm not 100% positive that they're base side. If we still have the film (which we just dropped), I'll take a closer look at it tomorrow. And I know that soundtrack down is evil, I've pointed it out and even showed them your reasoning for why it is evil, but they're just not changing it.

Posted by John Pytlak (Member # 331) on 01-17-2005, 10:18 AM:

Verify which side of the film is being scratched by looking at the surface of the film with specular reflected light.

As Brad notes, superficial emulsion-side scratches can be black on the screen, if the scratch only damages the topmost protective clear layer on the film. It's only when a scratch is deep enough to remove part of the magenta layer (green scratches) or magenta and cyan layers (yellow scratches) that you see a colored scratch.

Posted by Jacob Szewczyk (Member # 2513) on 01-17-2005, 12:26 PM:

I called up our head projectionist last night and told him to figure out whether or not they were emulsion or base scratches. I talked to him today and he said that they were emulsion side, and not base. I guess I was wrong.

Posted by Brad Miller (Member # 2) on 01-17-2005, 04:23 PM:

...and this is why you should never run soundtrack down. What happened was the film physically got scraped over the edge of the platter while it was taking up back onto it. Just be fortunate that it only lightly scraped, otherwise those scratches would be nice green or yellow ones!

You need to get down eye level with the edge of each platter and watch as the film takes up onto the deck. You've got at least one deck that is either scraping the film, or pehaps has a bent part such that every revolution of the deck it reaches up to give a nice "scrape" to the film. Super platters are notorious for this just like Potts/Strong platters are because the roller (as pictured below) does not have an adjustable height setting to prevent it. (Plus the designers are under the foolish belief that the edge of the film should be touching the deck the entire travel up to the film pack...not so! The film should not make contact with the deck until the very last inch or so before it lays flat up against the rest of the roll that is being taken up!) If you have the motor mount just a tad bit too high (to try and slow them down so they don't sling your prints across the booth), this happens.

The side facing toward the floor when you run soundtrack down is the emulsion, and in this picture you can see how it *can* scrape against the edge of the deck. It doesn't take hardly any pressure to put an emulsion scratch on a print, and after awhile (if not immediately) those black scratches will turn colored and your digital soundtrack will become unreadable and you will then be left with a badly scratched analog track to play for your audience. If you run soundtrack up and have the exact same physical roller/deck alignment issues, the worst thing you will see is black scratches on the right side of the image. Yes neither is acceptable, but at least running soundtrack up and having this problem occur is far less damaging than running soundtrack down.

You should read this review on ORC platters. It's basically the same thing as those piece of crap Supers you are running.

Note - not all platters are as poorly designed as the CFS Super/ORCs. Unfortunately all it takes is a couple of bad designs out there to convince the ignorant that all platters are evil. [Roll Eyes]

Posted by Monte L Fullmer (Member # 2797) on 01-18-2005, 01:57 PM:

Now, that some serious scratching going on with this ORC/CFS platter with that film laying down so close to the deck on takeup.

Little question: I went to that link of this platter, saw the double roller assembly where the film feeds back to the platter, and both of those top rollers being out of alignment, would this have been caused by a serious wrap or tension thingy to pull those rollers out like that, or was that a definite design flaw as with the whole machine.

Yep, I've wondered about those "dished" platters slinging film if they want to..

-never had the "opportunity" to work with these platters, and maybe just as so.

-thx Monte

Posted by Dave Macaulay (Member # 813) on 01-18-2005, 09:04 PM:

The roller feeding to the platter is adjustable on Strong Alpha platters, I don't specifically remember the setup on the AP type but I expect they're adjustable as well; manufacturing tolerances on the thing pretty much demand an adjustment. While some platters may come maladjusted as you describe - with film contact the whole way across the platter - that's not the right way and I've never set one up like that. The film edge should touch the platter a few inches from the film pack.