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Emulsion scratch found on roll - potential causes?


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#1 James Malamatinas

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Posted 17 September 2017 - 12:01 PM

I'm loading on a feature at the moment, we've just completed the second week and the production manager has come to us because one of the rolls has a scractch through the roll. I've attached an image. 

​We are shooting on the Arri LT, 3-perf, 24 fps @ 172.8 shutter. 

​I'm trying to help production understand how this might have been caused and to see if we there is anything we could have done to avoid this. Having not had a scratch turn up on anything I've shot I'm a little knew to the potential causes however it looks like this has definitely occurred prior to processing and therefore an issue with the camera or mag. .

​A couple of notes:

  • The roll in question was shot at 24fps, it was over or under cranked. 
  • ​The magazines had been scratch tested and shot on earlier in shooting before this roll with no issues. 
  • The lab has suggested it might be  a loop or take up issue, however the LT is fairly advanced at detecting both issues. At no point during the threading or running of the mag did it give a winding, buckle or take-up message like it usually does e.g. when the take-up side comes loose. I'm wondering if a similar type of scratch can occur in other cameras where there are fewer checks to prevent incorrectly sized loops or loaded mags and they are referring to this more generally rather than specifically to the LT?
  • The mag has been used twice since the roll where we got the error. We are awaiting the rushes on Monday to see if the error has occurred on these also .

 

If anyone could help narrow down what specifically the issue is that would be a great help. We have taken the mag out of circulation already but being able to give an exact explanation of what happened to the DP and production, as well as how we will prevent it reoccurring, would be well received. 

​If any AC's here could also share any systems they have for maintaining / checking mags during shooting then that would also be greatly appreciated. 

 



 

Attached Images

  • Emulsion Scratch_Crop.png

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#2 Robin R Probyn

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Posted 17 September 2017 - 01:06 PM

If it was through out the whole roll it would have scratched off alot of emulsion.. you would see this in the mag.. after unloading.. and if the gate the same.. you would see quite a bit of emulsion, that would be very obvious ..  the labs will always blame the camera.. I had various run ins with labs back in the day.. their mistake they always basically blamed the AC/gear.. not saying its the case this time.. but don't just believe what they say.. they will cover their arse at all times.. 


Edited by Robin R Probyn, 17 September 2017 - 01:09 PM.

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#3 Tyler Purcell

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Posted 17 September 2017 - 01:39 PM

I can't imagine it being the magazine itself. The film goes out the rollers straight to the sprockets and out the sprockets straight into the mag. SO there is no room for anything to "touch" there. Inside the magazine, the sprockets and rollers are tapered, so they aren't exactly suppose to touch anything in the center. Also since they're "rolling" most likely any issue you'd see wouldn't be a "fixed" line like that, it wouldn't be nearly that consistnet.

You can very easily run a dummy load in the mag and see how the film actually doesn't touch any 'edges' so it's nearly impossible for it to be scratched in the magazine.

I also can't imagine it being a loop issue, usually loop issues are inconsistent, they aren't just fixed like that throughout the entire roll.

In my opinion, the only way to get a "fixed" line like that is with something that is physically touching the film on a straight "clamped" component. There are only THREE clamping surfaces in the camera... the two sprocket guide clamps that hold the film on the sprockets and the pressure plate of the gate.

The film is held in place by it's edges, but the gap between the gate and the emulsion is very tight. A build up of schmutz in the gap in the bottom part of the gate where the pulldown happens, could cause an issue like that. It doesn't have to be very much because even though the chromed surface isn't touching the film where the image is, that gap is pretty tight.

One thing I always do when I shoot with cameras that need to be loaded is that after the first take, I run the camera a bit, open the door and give a twist to the film as it's going back into the magazine to see the emulsion and backing to make sure there aren't any obvious issues. After scratching the piss out of several rolls of film in my lifetime, from very simple issues that could have been resolved through a quick look, I do make it a priority. I however, mostly shoot with quick load cameras these days, so the only real spots of scratching are in the magazine anyway. So it's all about keeping the mags and gate/pressure plate clean.

Hope that helps and I look forward to seeing what the next rolls of film look like. I hope they come out fine and this was just a fluke.
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#4 Dirk DeJonghe

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Posted 17 September 2017 - 01:58 PM

If the scratch doesn't move left to right, it is most likely caused in the camera gate. A piece of crud may be touching the emulsion and may cause a pressure scratch, the film is 'exposed' maybe in one emulsion layer only, just by local pressure, there may not be any physical scratch where the emulsion is removed.


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#5 Dom Jaeger

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Posted 17 September 2017 - 08:07 PM

Easy enough to check the neg and see if it is an actual scratch, if so as Robyn said you should have noticed a lot of emulsion dust in the camera.

 

I don't recall ever having a scratch issue like that with Arricams at the rental house I worked for, they're pretty well designed to avoid scratching, as long as things are kept clean. A loop issue should have triggered the buckle switch as you say, and is more likely to produce intermittent scratch patterns. The sprocket loop guides only limit the film at the edges if I recall. Is this a maintained rental house camera?

 

You can easily do your own scratch test with the first few feet of a new roll. After rolling about 20 ft through, mark the film with a sharpie at the top of the gate so you can locate where a potential scratch has started in the camera transport path, cut the film where it leaves the mag, remove that length and check with a loupe for scratching. 

 

If it is the camera, it's most likely at the gate. You can easily remove the gate for cleaning on Arricams, as detailed in the manual (under aperture plate removal). The dust check button lets you do a quick gate check through the lens port. The other possibility is a film chip or something stuck in the magazine throat, but that's uncommon in my experience.

 

Sometimes there's no way of proving if it was the lab or something in the camera that dislodged after the roll went through. 


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#6 Simon Wyss

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Posted 18 September 2017 - 02:06 AM

If it were at the lab, the conditions needed to be identical to what you have here, namely the film located exactly against a reference edge with lateral pressure. The scratch you’re showing is a precisely drawn line, usually caused by a mineral particle or a burr. It is therefore not the lab but the camera and judged by the colour, the depth of cut, a grain of sand. Did you shoot outside? Windy days?


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#7 Dirk DeJonghe

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Posted 18 September 2017 - 04:27 AM

If it would be a physical scratch, the top layer (blue) would be (partially) removed by the scratch and you would see a blue line on the print. Look at the layers individually and look if only the blue,green or red layer is affected or a combination.


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#8 Robin R Probyn

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Posted 18 September 2017 - 06:27 AM

If it were at the lab, the conditions needed to be identical to what you have here, namely the film located exactly against a reference edge with lateral pressure. The scratch you’re showing is a precisely drawn line, usually caused by a mineral particle or a burr. It is therefore not the lab but the camera and judged by the colour, the depth of cut, a grain of sand. Did you shoot outside? Windy days?

 

Labs can scratch film..don't see the logic of your explanation TBH.. a scratch is a scratch .. yes something must cause it .. how do you come up with the grain of sand judgment .. because the line is sand colored  ??  

In the years I was a camera assistant in the UK.. 80,s.. the labs made many mistakes and always 100% tried to blame the camera crew.. until proven wrong .. 

 

Again I would say it should be very obvious .. a whole roll with a big scratch all the way through.. thats a big chunk of emulsion that has to go somewhere.. either bottom of the gate or the mag.. or the lab.. 


Edited by Robin R Probyn, 18 September 2017 - 06:34 AM.

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#9 Dirk DeJonghe

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Posted 18 September 2017 - 08:31 AM

A lab scratch is usually quite easy to identify, the rollers on the processing machine are about 40mm wide and the film gently moves from left to right on the roller. The main culprits for scratches in the processing machine are the squeegees where something may get caught. In this case the scratch will have an easily visible zig-zag pattern. If the scratch is steady and straight, it usually comes from the camera.


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#10 Robin R Probyn

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Posted 18 September 2017 - 09:52 AM

A lab scratch is usually quite easy to identify, the rollers on the processing machine are about 40mm wide and the film gently moves from left to right on the roller. The main culprits for scratches in the processing machine are the squeegees where something may get caught. In this case the scratch will have an easily visible zig-zag pattern. If the scratch is steady and straight, it usually comes from the camera.

 

 

Yes fair enough..:).. maybe Im a bit down on labs.. but really they used to blame all their mistakes on the gear and crew.. once they didnt fix the print properly .. so it was still changing sitting on a steinbeck..!! and they tried to blame me as the loader.. and no apologies .. I guess they have to be a bit nicer these days.. 


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#11 Simon Wyss

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Posted 18 September 2017 - 11:55 AM

Labs can scratch film.

 

In the years I was a camera assistant in the UK.. 80,s.. the labs made many mistakes and always 100% tried to blame the camera crew.. until proven wrong

 

In the years I worked at several labs as machine and hand developer I have seen camera originals scratch-ruined in processing machines. Once a 35mm color negative from a production waiting for the rushes, mate next to me at the ARRI completely lost nerves. Lab lost client, it was tough. A bent stop plate at the bottom of a tank reached the film, bent due to misalignment and too rough lowering of the racks into the tank.

 

When processing film by hand in spiral reels I had everything except scratches. Soon I got the knack and could deliver perfect originals. I had to close my own lab due to the dwindling market, not because of damaged film. Machinery can be devilish.

 

Evil as I can be I’d also suspect a conversion job on the camera. OP says 3-perf., let me suggest that there could be an issue with the gate. Still, a grain could stick around somewhere, if in the lower part of the gate, the film would carry gelatin traces with it. Possibly


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