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Flicker from Kino powered by genny


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#1 Jim Hyslop

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Posted 12 March 2009 - 08:25 PM

Hi,

I was 2nd AC on a short film a while back, and we shot a scene on location. One of the lights we used was a KinoFlo. Power was provided by a diesel trailer genny. When I watched the film, I noticed the Kino was flickering. Could that have been caused by the genny not generating exactly 60 Hz, or by the camera being slightly off-sync? Or would you have to see the shot to be able to comment?

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Jim
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#2 Ryan Thomas

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Posted 12 March 2009 - 10:26 PM

Unless you were shooting some strange shutter, I'm just going to take a stab at it and say that the genny's voltage was a little off. That could be culprit with the flicker. You would just have to adjust the voltage on the genny while you measure it with a voltage meter to make it correct.

Edited by Ryan Thomas, 12 March 2009 - 10:26 PM.

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#3 JD Hartman

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Posted 13 March 2009 - 09:20 AM

Only the Kino seemed to be flickering? Could be a bad tube. If the generator voltage was low, light from any Tungsten fixtures would have looked a warm on the monitor. Flicker is caused by power frequency not voltage.
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#4 Jim Hyslop

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Posted 14 March 2009 - 01:30 PM

I forgot to mention we were shooting on an Arri SR3, which has a fixed shutter.

Yes, only the Kino was flickering - the tungsten lamps were fine.

A couple of other factoids that may affect things: it was just above freezing, and we ran into problems with the battery later that day. Could the cold or a low battery voltage have affected the camera speed?

Edited by Jim Hyslop, 14 March 2009 - 01:31 PM.

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#5 JD Hartman

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Posted 15 March 2009 - 03:27 PM

In general florescent lights don't like the cold. Did it seem like the tubes took a while to reach full brightness. I can't comment on Kino's electronic ballasts, but most floro ballasts will have problems with low temperatures. Reliable operation at low temperature requires a different design.
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#6 Adrian Sierkowski

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Posted 15 March 2009 - 03:49 PM

Arri SR3 has a variable shutter... If you hold down the "Phase" button on the camera you can be certain of where it was set.
I would say perhaps cold on the floros and/or an older/bad tube.
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#7 Jim Hyslop

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Posted 16 March 2009 - 10:24 PM

Arri SR3 has a variable shutter... If you hold down the "Phase" button on the camera you can be certain of where it was set.

Oh. Good thing I was only 2nd AC :-) Thanks for the info. I've downloaded the manual but haven't had a chance to read through it yet.


So, the consensus seems to be either a bad tube or the cold. Is there any kind of test we could have run before shooting?

BTW, the flicker was fairly subtle - most audience members probably wouldn't notice it.

Thanks for all the replies!
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#8 Jamie Metzger

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Posted 17 March 2009 - 02:17 AM

Oh. Good thing I was only 2nd AC :-) Thanks for the info. I've downloaded the manual but haven't had a chance to read through it yet.


So, the consensus seems to be either a bad tube or the cold. Is there any kind of test we could have run before shooting?

BTW, the flicker was fairly subtle - most audience members probably wouldn't notice it.

Thanks for all the replies!


SR2 has a fixed shutter. There could be the possibility that the shutter was at a different degree, and it wasn't a safe angle. I know on the sr3 you can shoot 24/25/29.97, and if you were at 29.97, a kino would definitely flicker, as would HMI's.

Too many variables though. Ballast, and the tube seem more reasonable.
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