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Using Low Frame Rates as Special Efffect/Lighting Fix


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#1 Alain Lumina

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Posted 31 March 2010 - 11:59 PM

I recently saw some fascinating B+W stills shot in Russian city in very low light at night, the faces were sort of smeared to the sides, someone told me they were shot in film with very slow shutter speeds.

That made me think of a desert magic hour scene I want to do where a ghost approaches from a long distance, at first unrecognizable, until it nears and it seen to be the dead wife of the protagonist.

With a CP-16R and a "bow-tie" rotating shutter, I can reduce the shutter speed to I think 12 or 16 FPs, does this mean that, at , say, 12 FPS the shutter is open twice as long as at 24 FPS?

And maybe I can get that intentional smearing like very old movies.

And if the shutter speed is twice as long and I use 500T, could somebody offer a ballpark meter reading F stop which with a 2.2 lens which would be the farthest I could push it? A reading of 1.2? 0.9?

Understand I'm looking for an extreme effect here, don't care if it's grainy as hell... I'm more thinking of how far can I push it and still get any image at all that's recognizable.

And what about the faster B+W stock from Kodak, which I think is 200?
Could it maintain recognizability of objects in the frame as well as 500T?

Analog degrades gracefully.
All ideas welcome, thanks!

Edited by Alain Lumina, 01 April 2010 - 12:02 AM.

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#2 Adrian Sierkowski

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Posted 01 April 2010 - 09:17 AM

You shutter speed would be slower than 24fps (on a 180 degree camera @ 24fps you'd have 1/48th of a second shutter, at 12 fps you'd have 1/24th). As such things moving would blur and you would need 1/2 the amount of light for the same exposure; or simply put you get an extra stop. So if you were at a F4, you're now be shooting at a F5.6 to keep the same exposure if you slower the camera down (essentially you could rate your 500T @ 1000T, though 800 would probably yield better results). And 200T film, @ 12fps coudl be treated the same as 400T film for those shots.
The problem is that the footage would be sped up if you transferred or projected the footage @ 24fps, so you'd loose the effect and instead wind up with a clip which is 50% faster. You'd need to speak with the post house about transferring the footage @12fps if that's possible-- I am not 100% sure on what'd happen if you simply transferred @24 and slowed it back down to 12 in post, however.

What would be better to do, though not possible on a lot of cameras, would be to keep the FPS the same, at 24, but change the shutter angle in order to decrease the shutter speed. Though off of the top of my head I don't know what angle you'd need to change to to get the same effect as a 12fps imageĀ .
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#3 John Sprung

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Posted 01 April 2010 - 02:17 PM

If you just step print to 24, the result is you don't have enough frames per second to get the illusion of motion. Instead, you have an extremely fast slide show. A friend of mine did that like 40 years ago, both at 12 and 8 fps, with step printing. It would be interesting to try Arri's Relativity software on that material. My guess is, it might give you decent motion.




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