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Old November 29th, 2008, 08:21 PM   #1
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big problem -- shutter at 250, exposure won't lock!

I'm shooting 60i in the TV mode, and wanted to try a higher shutter speed so I can experiment with slowmo.

I white balanced, and started shooting -- and lo and behold, the exposer (even though I have it locked) kept drifting up and down, in a pretty much predictable manner, with the white balance changing dramatically. I shoot with zebras and I can see the exposure going up, then going down and all the zebras disappear, the shot gets very orangy, then back up, just drifting back and forth, whenever I shoot at 250th of a sec shutter speed or higher.

Any ideas? Anyone experience this? I am shooting a lot in Dec and hate to have to drive all the way down to Orange County Monday morning and hope they can get it back fast (they usually do).

But the white balance won't stick, the exposure it just up and down. I'll capture a little and upload it later tonight so folks can see. It's a major problem... :=(
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Old November 29th, 2008, 09:28 PM   #2
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Here's an example of the white shift/exposure that was happening consistently whenever I'd shoot at 250th of a sec or above:

http://www.mostlymagic.tv/white_shift.mov

See the color shift and exposure shift back and forth throughout? Seen anything like this before?
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Old November 29th, 2008, 09:49 PM   #3
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Hi Jeff...............

Don't shoot under flouro's at anything above 1/60th.

That's definately flouro lighting and it's definately strobing.

Not as fast as it can, and not giving rise to the banding one would expect, but that's gotta be a flouro problem, not a cam problem.

1/250th = 4 X 60 Hz plus a bit which is why the colour shift is so slow.

That's my story and I'm sticking to it!


CS

PS: The subject (problem) has been covered extensively here on DVinfo, use the Google bar at the bottom of the page to search for relevant key words, you'll find a shed load of references.

Last edited by Chris Soucy; November 30th, 2008 at 08:45 PM. Reason: +
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Old November 30th, 2008, 12:23 AM   #4
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Chris -- thanks so much. That really explains it. I did a search and found a ton on the subject, just as you suggested. I have been shooting in this rehearsal place on and off and never encountered this, but have never shot above a 60th of a second. Only today shooting at 250 am I seeing this problem. In general I never shoot under flouro because I light everything. This is a good lesson, and fortunately it was just a "for fun" thing, not a paid job.

Thanks for the quick response.
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Old November 30th, 2008, 10:01 AM   #5
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Jeez... and I thought it was just indoor smog. (grin)

Seriously, I was not aware of this so I learned something today.

Chris knows everything. (grin)
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Old November 30th, 2008, 08:46 PM   #6
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Aw, shucks...........

You say the nicest things Tripp.

Glad to be of service Jeff.


CS
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