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I got a flicker in my CP - GSMO


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#1 rbg

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Posted 31 March 2006 - 06:42 PM

Hey-

I just shot a spec music video on my CP - GSMO and during the transfer, both the colorist and I noticed a flicker in the footage. It happened on multiple lenses, multiple mags, and I used multiple batteries, so I'm thinking it's something electronic, something to do with the regulation of the motor speed. It's not super bad yet and is only really noticible in the whites, but the colorist said all of the levels were spike-ing. I want to save it before it gets worse. The camera is like one of my kids. Does anyone have experience with this in a Cinema Products camera, or a GSMO to be exact??? Help??

Thanks

RBG
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#2 Chris Keth

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Posted 31 March 2006 - 07:33 PM

Hey-

I just shot a spec music video on my CP - GSMO and during the transfer, both the colorist and I noticed a flicker in the footage. It happened on multiple lenses, multiple mags, and I used multiple batteries, so I'm thinking it's something electronic, something to do with the regulation of the motor speed. It's not super bad yet and is only really noticible in the whites, but the colorist said all of the levels were spike-ing. I want to save it before it gets worse. The camera is like one of my kids. Does anyone have experience with this in a Cinema Products camera, or a GSMO to be exact??? Help??

Thanks

RBG



Sure it's not flicker from a light source or sources on the shoot? I don't see any way flicker like that could be your camera.
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#3 Tim Carroll

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Posted 31 March 2006 - 09:27 PM

Hey-

I just shot a spec music video on my CP - GSMO and during the transfer, both the colorist and I noticed a flicker in the footage. It happened on multiple lenses, multiple mags, and I used multiple batteries, so I'm thinking it's something electronic, something to do with the regulation of the motor speed. It's not super bad yet and is only really noticible in the whites, but the colorist said all of the levels were spike-ing. I want to save it before it gets worse. The camera is like one of my kids. Does anyone have experience with this in a Cinema Products camera, or a GSMO to be exact??? Help??

Thanks

RBG



Had that problem with a Bolex EBM a few years ago. Never did get it solved. In retrospect after having discussed the issue with many different folks, I think what happened is that the gear train just had too much slop in it from many years of use, and the way the Bolex motor works, with a crystal sync (we had a Tobin sync on it) the motor was regulating itself by slightly speeding up or slowing down to keep at 24fps, and that combined with the slop in the gear train, caused the shutter to "bounce" which cause the exposure to flicker. It did this under tungsten lights as well as outdoors. When we took the crystal sync off, and just ran the camera at the non-crystal 24fps, the speed drifted around a bit, but the shutter "bounce" and the resultant flicker went away.

If you have a strobe, you should be able to see if the shutter is "bouncing", which would be one thing that could be causing the flicker. What shutter "bounce" looks like with a strobe, is if you set the strobe at 24fps and shoot it at the rotating shutter (I am assuming your camera is crystal sync) you should be able to freeze the edge of the shutter blade as it passes the gate. If the camera is crystal sync and everything is working perfectly, the edge of the shutter will freeze in one position, say halfway through the gate. With "bounce", you will notice the shutter will freeze for a second, then drop down further over the gate, then jump back up to the middle again, freeze, drop down, jump back up, as if it were bouncing. This causes shorter exposure on one or a few frames and longer exposure on one or a few frames, back and forth, hence the flicker.

-Tim Carroll
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#4 Robert Hughes

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Posted 31 March 2006 - 09:38 PM

You didn't happen to be shooting under fluorescents or mercury/sodium vapor lights, did you?
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#5 Ralph Linhardt

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Posted 31 March 2006 - 10:44 PM

I also have a GSMO and have had trouble with flicker. sometimes i :( f the mag does not set right when you put it on and mess up the loop it can drag when it runs. Also, even the best GSMO runs about 3 to 5 degrees loose on the shutter becuase of the motor design. But with that all said it is most likely in the electronics. As you know there are no more spare chips for the GSMO so if your drive chip is flaky you will need to find someone to put a new drive system in it. Try AZ Spectrum in NY or Ian Love in LA He works at Clairmont Camera. If you ever want sell any GMSO stuff let me know.

Good luck!

Ralph Linhardt

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#6 rbg

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Posted 01 April 2006 - 01:34 AM

Sure it's not flicker from a light source or sources on the shoot? I don't see any way flicker like that could be your camera.


Unfortunately, I am sure it wasn't from light sources, as I was shooting outside with a stationary bounce. Nothing was moving.

RBG

Had that problem with a Bolex EBM a few years ago. Never did get it solved. In retrospect after having discussed the issue with many different folks, I think what happened is that the gear train just had too much slop in it from many years of use, and the way the Bolex motor works, with a crystal sync (we had a Tobin sync on it) the motor was regulating itself by slightly speeding up or slowing down to keep at 24fps, and that combined with the slop in the gear train, caused the shutter to "bounce" which cause the exposure to flicker. It did this under tungsten lights as well as outdoors. When we took the crystal sync off, and just ran the camera at the non-crystal 24fps, the speed drifted around a bit, but the shutter "bounce" and the resultant flicker went away.

If you have a strobe, you should be able to see if the shutter is "bouncing", which would be one thing that could be causing the flicker. What shutter "bounce" looks like with a strobe, is if you set the strobe at 24fps and shoot it at the rotating shutter (I am assuming your camera is crystal sync) you should be able to freeze the edge of the shutter blade as it passes the gate. If the camera is crystal sync and everything is working perfectly, the edge of the shutter will freeze in one position, say halfway through the gate. With "bounce", you will notice the shutter will freeze for a second, then drop down further over the gate, then jump back up to the middle again, freeze, drop down, jump back up, as if it were bouncing. This causes shorter exposure on one or a few frames and longer exposure on one or a few frames, back and forth, hence the flicker.

-Tim Carroll


I took it into George Zorzolli at Optical Electro House in Culver City. He's gonna check it out. What you're describing sounds like what is happening, especially the part about the exposure jumping around, frame to frame. Damn! I hope he can fix it. I'll post his results.

Thanks for the info. Tim.

RBG
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#7 Chris Keth

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Posted 02 April 2006 - 02:41 PM

You didn't happen to be shooting under fluorescents or mercury/sodium vapor lights, did you?



Nope, that was my first question to him.


That is kind of a strange problem. I've never heard of anything like it.
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Metropolis Post

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