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Lighting for 120fps RED CAM


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#1 Zac Halberd

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Posted 19 May 2008 - 06:40 PM

Shooting some models jumping on a trampoline in a small studio in slow motion with the Red Cam (windowed mode) using superspeeds. The backdrop is solid white, and the room is 30ft by 30ft and about 20ft high.

Basically I want the models to be evenly lit and quite fresh and bright with a slight rim light. However we're shooting at 120fps HD.

Am going to be booking the lights tomorrow, and I'm at a loss for how much firepower I'm going to need. I always like to start with more watts than I think I'm going to need and then work from there, but we're on a very tight budget.

I thought about a 2k on each side of the model through a silkscreen, a 2k above and slightly behind the model clamped to the ceiling for rim, and then another diffused 2k to fill. I also have a redhead kit standing by.

For some reason, I'm thinking this will not be enough light. That old gut feeling is nagging at me. I know HD is quite sensitive, but I've never shot at 120fps before.

Anyone here have any experience shooting high-speed HD?

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#2 Adrian Sierkowski

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Posted 19 May 2008 - 06:44 PM

What ASA will you be rating the camera @?

And yes, I would say you'll need a lot more than the lights you have listed.

I don't have my ASC manual with me, but the compensations are in there, I believe; I think it's 5X more light (120fps/24fps?) but memory doesn't serve properly right the now.

Don't forget the RED has a native ASA of 320; but you can change that via metadata. There was an interesting test awhiles back on reduser about rating the redone; and it appeared that the higher ASA you set, the better for highlight detail @ the expense of shadow noise?

Edited by Adrian Sierkowski, 19 May 2008 - 06:48 PM.

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#3 Zac Halberd

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Posted 19 May 2008 - 06:58 PM

Thanks for that dude. I do remember from the short we shot last on the Red that the DoP was complaining about the shadows being noisy. Fortunately we won't have to worry about that as it's all going to be very white, with no shadows. perhaps rating at a higher ASA will work in my favour in more ways than I thought.

It looks like I'm going to have to go with flicker free HMI then. I wanted to stick with tungsten, as then I could use the house lights, as well as avoid the paranoia of flicker from HMI. I've not dealt much with high speed shooting.

What if I replace the 2k's with 4k HMIs? I want the light quite soft as well, so we're talking full diff here. That's basically three 4ks hitting the model from less than 15 feet away but through full diff.

This is going to cost a bit.
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#4 Mitch Gross

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Posted 19 May 2008 - 08:00 PM

Double the speed requires double the light. Go from 24fps to 48fps is one stop. From 48fps to 96fps is one more stop of light (it's log, not linear math). So 120fps will eat about 2.3 stops of light. The base ISO of the RED One is 320, which means that you'll now be shooting with the equivalent ISO of about 64. So yes, you will definitely need much more light than you were planning.

Do not worry about flicker as long as you have flicker free HMIs. At only 120fps you will not have to worry about it. It is only with extremely high frame rates that lights will begin to seriously flicker. Same goes for flos. Don't use magnetic ballasts like in most household fixtures, but Kinoflos should be just fine. I think your 4K HMIs will do the trick. Perhaps you should consider bouncing the lights instead of punching through diffusion, as that will give you a much softer source.
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