Film-Tech Forum ARCHIVE: Diagonal film scratches

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Posted by Sarrah Halstead (Member # 5670) on 09-20-2010, 02:24 PM:

I am having diagonal film scratches. Sometimes they are the majority of the frame but lately the very clearly stop half way into the frame. They are usually on the soundtrack side of the frame, but I have one now that is on the opposite side. They are often green and black or just black. The reason I do not think it is the platters is because they are exactly the same from policy trailer to final credit with no change. I have a simplex 35 projector with a Strong x-90 lamphouse. I have a Strong Alpha platter system. Any input is helpful since I am at a total loss and have been unable to recreate them.

Posted by Donald Brown (Member # 5427) on 09-20-2010, 03:59 PM:

Sarrah:
While it would be a good idea to check the film path from the platter, through the projector, and back to the platter for any source of contact with the surface of the print, what I have encountered most frequently as a source of diagonal scratches on either side of a print is misalignment between the platter and the make-up table when the print is assembled. If the surface of the film (the "frame" of the picture) is contacting the platter deck as the reels are assembled onto one of the decks, this may be the source of the scratches. The point that you make that the scratches only extend half way across the frame suggests that this is the area in diagonal contact with deck as the print is being put together.
The tension on the film at the make-up table, combined with the rapidly rotating deck surface at the platter, can produce these scratches if the roller alignment is incorrect and the film contacts the deck other than on it's sprocket edge.
The colored abrasions are affecting the emulsion surface; abrasions to the base would appear as dark lines.
Watch the make-up procedure when your next engagement begins and adjust the alignment between the table and the platter if necessary. That is a very easy fix!

Posted by Joe Redifer (Member # 3) on 09-20-2010, 04:01 PM:

Sounds like you got the take-up roller on the platter twisted, the one that leads directly onto the takeup deck. The emulsion side of the film (the outside when wound on a platter soundtrack up) was rubbing against the cocked roller which was facing inward towards the platter tree, thus the majority of the scratches are on the soundtrack side. 99:1 this is how it happened. There is a 100% chance that it got scratched on a roller as diagonal scratches can't really happen any other way unless you have an old Christie platter and drop the cluster below the bottom deck, and then they would be base scratches...

Posted by Sarrah Halstead (Member # 5670) on 09-20-2010, 05:32 PM:

It is not happening during make up. I build every print and they are not scratched the first showing. I will try to recreate it tomorrow with turning the roller incorrectly as was suggested. I agree that it must be a roller somewhere, and this would make sense.

Posted by Randy Stankey (Member # 64) on 09-20-2010, 06:27 PM:

One of most difficult things to trace down are scratches caused by problems in the take-up part of the system.

The damage occurs AFTER the film has played. The film is wound up on the take-up platter or reel but it doesn't manifest itself until the NEXT time the film is shown. By then, it is too late, the damage has already been done.

If you have several people operating the equipment, any one of them could have been responsible. Even if a particular person isn't directly responsible for causing the damage, he could be indirectly responsible because he did not properly monitor the film as it pays out, plays and rewinds throughout the program. If he had been on the ball he might have caught the problem and fixed it before the entire movie was damaged.

It only takes one person to mess things up for everybody. I could come in to work the afternoon shift and misthread the projector just one time and scratch the film all to hell. You come to work on the evening shift and take over for me as I go home. But there lies the scratched film on the platter and you don't even know it. If I'm a part timer or a fill-in, you might not see me again for a week.

Then, on the next round, you play the film that I screwed up. You are the one who gets called on the carpet for the damaged film. You are the one who has to chase down the cause. All because, ONE TIME, I got sloppy.

I'm not yelling at you as much as I am sympathizing with your situation but I am also giving you a little permission to hold your fellow employee's feet to the fire and make them pay attention to their work so this kind of thing doesn't happen again.

Posted by Gordon McLeod (Member # 33) on 09-20-2010, 06:29 PM:

often a diagonal scratch is caused by the film getting mistrheaded between a keeper and a rooler so it is pinched on a flange

Posted by Monte L Fullmer (Member # 2797) on 09-20-2010, 10:14 PM:

Bet you had many brain wraps with your setup.

What happens is the rollers that help feed the film back to the deck are bent up slightly due to the sudden tightening of the film when the wrap hits, and when the film is feeding back to the deck, the rollers, since they are not square with the film, tend to allow film to ride towards the side of the roller to where it's riding on the flange of the roller itself..and this causes the diagonals since the roller cannot swivel and keep aligned with the film at all times.

Posted by Jonathan Smith (Member # 5609) on 10-09-2010, 03:36 PM:

I don't know what to say about "soundtrack side" scratches.

I think in terms of emulsion side or base side. Assuming you run soundtrack up, the scratches are probably platter scratches on your print that has the diagonal scratch on the "non-soundtrack side."

I can't explain the soundtrack side. I think, in that case, one of the prior posts would be right.

But, how are you determining "soundtrack side," on screen? Remember the image is flipped horizontally AND vertically during projection.

Emulsion is facing INTO the lamphouse, not towards the lens and screen during projection. This is confusing, because it is the OPPOSITE of a 35mm slide, or a camera original slide or negative. When they contact print film, the emulsion is held in contact to maximize sharpness. So negatives project or print emulsion out, master positive emulsion in, internegative emulsion out, and print emulsion in.

I'm sorry if that is confusing. Dyes that form the negative face out where light is focused on the image; interpositives and prints have dyes facing IN to CONTACT the dyes they are copying during printing (also during projection).

I think you were evaluating prints on the screen (side towards YOU standing on the thread side of the projector in the booth) but that is actually a reversed, upside-down image of the film in the gate.

If you gently hold the edges of the film in the intermittent loop, you can see an upside-down, reversed image I am talking about from between the film and the screen.

Anyway, my own personal experience with this was caused by several prints last year being scratched. No one else gave a shit. I was thinking synch marks (from pulling film tight on a reel) because they are roughly horizontal on sideways-running 35mm STILLS.

So that didn't make sense because they were more vertical, but even there not quite. Diagonal lines aren't synch marks.

Finally, one day, I asked a fellow projectionist at the other IATSE UNION theatres I secretly worked at, who had been doing projection since before my GM at Cinemark was born, about the problem.

He said, "With a strong platter, that is probably platter scratching. The film is being incorrectly threaded back to the takeup [platter film winds back onto after projection] platter."

"No way!" I said, "No one in the booth, besides the managers, would make that mistake."

Well, sure enough, I walked into the booth one day, and Drew, the Usher who had "some projection experience" at his former Cinemakr job with different platters Christie and maybe different projectors had FIVE DIFFERENT PROJECTORS threaded that way. . .

I stopped a lot of movies mid show and ran around the booth to check all thirteen film projectors. After the ensuing panic ended, I did check the final mis-thread, and it actually DIDN'T touch the platter in a way that could scratch the film. My hunch is the tension varies depending on which platter was taking up, how long the movie is, how far into the movie, and maybe how crooked the platter is to cause the film to bow down just enough to scrape against metal.

Am I needlessly plugging the Union? No, I'm not, because my 27 y.o. GM didn't have the funds to PAY anyone more than a quarter above minimum wage. That precludes 20-year veterans with any self-respect from working in a chain theatre environment. Frankly, they didn't deserve my fixing the problem, because, on more than one occasion, said GM said that the scratches were "fine."

So, double check that your film is not "shaving against the grain" (soundtrack facing in the direction platter is spinning to).

Make sure it's always facing INTO the spin.

Posted by Chris Slycord (Member # 4239) on 10-09-2010, 09:09 PM:

quote: Jonathan Smith
But, how are you determining "soundtrack side," on screen? Remember the image is flipped horizontally AND vertically during projection.

Emulsion is facing INTO the lamphouse, not towards the lens and screen during projection.

Everywhere I've worked, soundtrack side referred to the portion of the image closest to the soundtrack (ie the part that shows up on the extreme left portion of the screen).

The scratch can be soundtrack side, non-soundtrack side, anywhere in-between and with all of those possibilities you can have them be on the emulsion or base sides.

Posted by Louis Bornwasser (Member # 3063) on 10-09-2010, 10:28 PM:

You get what you pay for.

If any cinema can't pay a living wage for a professional, then they are already closed; they just don't realize it yet. Louis