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Exposure compensation for high speed cinematography


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#1 Ashley Barron

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Posted 19 May 2009 - 12:54 AM

Hi there,

I wasn't sure in which forum this topic would be most appropriate, so here I am.

I'm getting myself confused by trying to figure out what exposure compensation is required to shoot in high speed frame rates.

Do you need less light or more light for this? Therefore, would you open up or close down?

And while I'm at it, when someone says "add more stop" that means open up or close down?

Any advise would be great.

Cheers,
Ash.
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#2 Rob Vogt

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Posted 19 May 2009 - 08:41 PM

The faster the frame rate, the less time the film has to expose and thus you will need more light at higher frame rates. When you double the frame rate you need one more stop so 24 fps if you're at a 5.6, for example, then at 48 fps you will have to open to a 4.

Edited by Rob Vogt, 19 May 2009 - 08:41 PM.

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#3 Chris Keth

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Posted 20 May 2009 - 06:41 PM

And while I'm at it, when someone says "add more stop" that means open up or close down?


I've never heard of anything instructing their AC to "add more stop" when they want to open up or close down. They'll always give you a number.

"Add more stop" usually means to light to a deeper (higher number, smaller iris, more light) stop. What the camera does in response to that can vary. You might be shooting high speed for a shot and NDing to keep the same stop for the rest of the scene for example.

Edited by Chris Keth, 20 May 2009 - 06:44 PM.

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