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Red flashes on the neg.


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#1 Dan McCormick

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Posted 21 March 2007 - 12:48 PM

Hi

I recently loaded a short (student) advert shot on the Arri SRII Super 16mm camera. When it came back from the telecine there is a red flash on the right edge of the frame, which only comes up at the end of each take. Usually it flashes briefly, disappears for a second then returns for the last second or so of the take. I didn't notice any problems when loading or unloading, and the same mag has been used since without showing the same problem.

Any ideas what could have caused this?

Thanks

Dan McCormick
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#2 Michael Collier

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Posted 21 March 2007 - 01:35 PM

While I am new to film, it seems to be a typical thing. Every one of my 16 reels had the same flash on the head and tail, along with the flash everytime I opened the door to check loop etc in the middle of the mag (I did run some extra feet before I opened the door, so I didn't loose any needed footage)

I think on the head obviously there will be some fogging from light on its way into the mag before it really hits the light baffle (I am sure small amounts of light can bounce back and forth up the film for at least a few inches, sort of like a poor fiber optic)

But you say it happens on every take? That is more pecular. I could see two things possible. One would be the shutter is not properly parking itself when you stop. That might let light into the gate, which then bounces around and exposes film above and below the take. This would have been more obvious though, since if its not parked, you'd likely not see anything through the viewfinder while not running, something I am sure you'd be more upset over than a little flashing before and after.

The other possibility is did you open the door after every take to check the film threading or gate? I have heard the reason the flash is red is because the light hits the emulsion at an angle, and so more of the red layer gets exposed? Interesting if thats true...anyone know for sure?

the reason I'd suspect the door is because of the position of the flash. Every camera door I have ever seen is on the right, so you'd be exposing the right side of the film. since lenses flip the image upside-down, the right side becomes the left when view (this is correct right? somebody correct me if I am wrong on that), so it seems that any light leak would have to come from the side of the camera with the door.

Just a few ideas. Id suspect the latter one, but maybe someone on here with more experience would know. Assuming the camera works, the only time I saw the effect you describe is on the head, tail and every time I opened the door. If it is all you need to do is run a few seconds before opening the door and run a few seconds after.
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#3 Dan Goulder

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Posted 21 March 2007 - 01:52 PM

I recently loaded a short (student) advert shot on the Arri SRII Super 16mm camera. When it came back from the telecine there is a red flash on the right edge of the frame, which only comes up at the end of each take. Usually it flashes briefly, disappears for a second then returns for the last second or so of the take. I didn't notice any problems when loading or unloading, and the same mag has been used since without showing the same problem.

Any ideas what could have caused this?

Light flashes, pulses in luminance, or "reddish" frames at the beginning and end of takes are all a normal part of shooting film. Normally you would just edit those frames out. Since these flashes aren't happening in the middle of your takes, the camera appears to be working properly.
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#4 Nick Mulder

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Posted 21 March 2007 - 02:16 PM

Light flashes, pulses in luminance, or "reddish" frames at the beginning and end of takes are all a normal part of shooting film. Normally you would just edit those frames out. Since these flashes aren't happening in the middle of your takes, the camera appears to be working properly.

But he said they were coming from the side of the frame only. It doesn't sound like a camera winding up to speed to me.

I thought red frames usually were associated with light hitting the neg from the side, and not simply over exposure that you'd get from a camera winding up ... Does the SRIII do this ? I'm still learning, interested to find out what it is ...
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#5 Dan Goulder

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Posted 21 March 2007 - 02:30 PM

But he said they were coming from the side of the frame only. It doesn't sound like a camera winding up to speed to me.

The key point is that those flashes are at the end of takes, which is normal. The situation would be entirely different if they occured in the middle of, or throughout the takes.
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#6 Sam Wells

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Posted 21 March 2007 - 03:14 PM

It sounds like a small light leak probably caused by improper seating of the mag.

You see it at the end of takes because the film is "parked" at that time.

If it's the seating issue, it happens on 16SR's the mag runs and looks ok but is not locked all the way in proper position.

-Sam
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#7 Michael Palm

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Posted 21 March 2007 - 04:53 PM

I had the same problem on a 16mm SR-II, it was a light leak. Check the mag.
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#8 Sam Wells

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Posted 21 March 2007 - 05:23 PM

As it only happened one of the times on the same mag - and due to where the problem was I'd strongly suspect the seating issue (you wouldn't be the first second or third person this has happened to).

That lock *must* be pressed forward after the mag has been put in place.

-Sam
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#9 Dan McCormick

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Posted 22 March 2007 - 07:10 AM

Thanks for the help everyone.

From what I know of the camera and using it since the mag not being locked makes most sense to me. I finished loading a 10 minute short on the same camera last week, hope it doesn't happen again!
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#10 Chris Keth

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Posted 26 March 2007 - 12:17 PM

This is probably a magazine leak. Since the film is emulsion in, the flashes are red because the light has passed through the red-orange base before exposing silver.
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#11 Jonathan Bowerbank

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Posted 26 March 2007 - 11:26 PM

I hope you're taping the edges of the closed mag to prevent any light leaks. With crappy school equipment, this has been a common occurance.

You said it happens "for a second", is that literally speaking a full second, or do you mean just a few frames here and there. If it's just a few frames at the beginning then at the end, it's normal and there's nothing to worry about.
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#12 Terry Mester

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Posted 27 March 2007 - 09:33 PM

Dan, did you check the left side of the Negative to see if there was any light leakage on that side (between the Perforations)? The light would either be going through the Base Side or the edge of the Film. The Red and Green Emulsion Layers contain Masking Dyes which absorb some Green and Blue Light, and this is why the light leak appears Red on a Negative. It would be White with Reversal Film. You can very easily seal the connection between the Magazine and Camera with Aluminum Foil. Simply fold up a piece of foil about three or four layers thick -- to the size necessary to wrap around the connection. I would recommend that every Cinematographer seal up the Magazine connection as a prudent precaution against light leaks. It's better to be safe than sorry!
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#13 Andrew Koch

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Posted 28 March 2007 - 02:02 AM

It might be a mag leak. Where did you shoot this footage? Was it outdoors in the bright sun? Did you tape up the mag to prevent light leaks? I also have a question for the last poster. Why do you recommend aluminum foil to cover the seal between the SR mag and the body? Couldn't the reflective surface of the foil be a problem, possibly bouncing light into the camera, mag, etc...
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#14 Chris Keth

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Posted 29 March 2007 - 04:53 PM

Dan, did you check the left side of the Negative to see if there was any light leakage on that side (between the Perforations)? The light would either be going through the Base Side or the edge of the Film. The Red and Green Emulsion Layers contain Masking Dyes which absorb some Green and Blue Light, and this is why the light leak appears Red on a Negative. It would be White with Reversal Film. You can very easily seal the connection between the Magazine and Camera with Aluminum Foil. Simply fold up a piece of foil about three or four layers thick -- to the size necessary to wrap around the connection. I would recommend that every Cinematographer seal up the Magazine connection as a prudent precaution against light leaks. It's better to be safe than sorry!


That's really not a good idea. Any camera shoddy enough to need this treatment shouldn't be used until it's PROPERLY fixed, period. No camera should ever need this and one that does probably has other far worse problems, because it's been abused.
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#15 Terry Mester

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Posted 29 March 2007 - 05:31 PM

Why do you recommend aluminum foil to cover the seal between the SR mag and the body? Couldn't the reflective surface of the foil be a problem, possibly bouncing light into the camera, mag, etc...


The nature of Aluminum Foil enables it to fit snugly and firmly around the shape of the Mag / Camera mould. You wouldn't likely need tape to hold it in place. If folded up to 4 layers thick, it should also last a very long time -- thus saving you from wasting time having to constantly make a new one or peel off tape. As long as the Foil extends a good 1/2 centimetre beyond each side of the seam between the Mag and Camera, no light should be able to reach and enter the seam. This is better than wasting a foot of Film each time you start the Camera to get fresh Film out of the Magazine. A wasted foot here and there adds up fast.
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#16 Terry Mester

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Posted 29 March 2007 - 06:19 PM

That's really not a good idea. Any camera shoddy enough to need this treatment shouldn't be used until it's PROPERLY fixed, period. No camera should ever need this and one that does probably has other far worse problems, because it's been abused.


You are technically correct, but what is a cinematographer on a low budget to do. If it's not their Camera, they're not going to spend their money to repair it.
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#17 Chris Keth

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Posted 30 March 2007 - 01:01 PM

You are technically correct, but what is a cinematographer on a low budget to do. If it's not their Camera, they're not going to spend their money to repair it.


This is true but if you're renting a camera, you should be responsible enough to whomever provide the budget to insist that the camera be in good working order.

The only way I would agree with your soluion is if you're borrowing a camera for free.
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