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Urgent help with slowmotion on Arri 416 needed!


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#1 Fabian Prell

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Posted 27 October 2009 - 11:07 AM

Hi,

I am shooting a short film in 3 weeks and need to book all the lighting equipment pretty soon. That will be dependent on some technical info I have difficulties gathering. The scene is the following:

There is a slowmotion scene at night in the woods. Its sort an imaginary fight of a Samurai and some of his martial arts moves withe sword are in slowmotion. The two main lightsources will be light from a fire for the front of his body and a moonlight (HMI) as backlight. Maybe some Kinoflo's and Dedo's as fill-light to get minimum exposure.

Usually I would go by the rule and say: for every 25 fps I go up (so 50fps) I loose 1 stop. (or from 24 to 48 in Amercan productons and features).

We plan on shooting at 75 frames per second (with the 416) or if we get the 416 plus HS with as much as we can with the light we have (up to 150fps).

Usually the lightloss could only be compensated by aperture and the strength of the light source.

Now I've heard that the lightloss can also be compensated by adjusting the shutter angle. Logically that would mean more motion blur though.

How far can I go with that before it gets blurry and how many stops can I compensate with it? The shutter can go from 45 degrees to 180 degrees standart as far as I know.

The problem is..I know I know... I don't have time for tests.. so I need to calculate it precisely and adjust the lights on the day...

Can anyone help me with this? Experience with slowmotion shoots on film?

The shoot will not have any ramping, just set framespeeds.

Many thanks!

Fabian
Cinematography
LCC London
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#2 Scott Fritzshall

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Posted 27 October 2009 - 11:59 AM

You can't really open up the shutter any more in order to compensate for light loss. If you were shooting on a digital camera that had an electronic shutter, you could set the "shutter angle" to 360 and gain an extra stop, but you can't do this on a film camera. You're going to need to shoot on a fast film stock, with fast lenses, and you're going to need to crank your lights. There's not too much else you can do.
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#3 Edgar Dubrovskiy

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Posted 28 October 2009 - 06:00 AM

Light for 150 fps (or whatever will be the biggest frame rate) and not for 25 fps.
If budget allows, of course. Maybe do only mids and close-ups at high speed for that matter.
And then just play with aperture or NDs on lights for normal 25fps.

Just out of interest - you renting from Arri Media?
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