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Double Diffusion Scenario


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#1 Daniel John Lee

Daniel John Lee

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Posted 27 March 2012 - 03:49 PM

Bit bored so I guess I'll throw this out there because I find it interesting.

Strangely... I spend some time pondering this even though I'm sure I must have put it to the test on at least one shoot. But I can never remember because it seems the time always gets away from you on the day and it's hardly something that's going to be debated in the middle of a working day.

Anyone who uses overhead softboxes with two layers of diffusion will get the question from their rigger or I guess it might be lighting grip in the States I don't know. They want to know where to position those scaffold middle bars for the 12x12 textile or something. I'm sure some of you gaffers out there will relate.

So the task is to get the softest light, losing the hot spot as much as possible by using two different diffusion layers. Lets say they're the exact same diffusion for the first thought. So 216 or something similar. That doesn't matter for this scenario I shouldn't think.

So we know... the closest diffusion, I'll call it the final diffusion works best for us as close as we can get it to a subject.

Now the intermediate middle diffusion, following a similar logic closer to that final diffusion as opposed to closer to the light is better for us.

Lets say we're actually flush to the final diffusion. That's not best because it's just like one denser single diffusion. But as soon as we start moving it closer to the light slowly we begin to reach our softest point. If we travel too much we're only going to start seeing the light hotspot again.

So I know from my own experiences. It's common to do this intermediate diffusion around about two thirds distance from the light to the final diffusion. It's certainly soft enough and you don't get DPs question it.

But the purpose is to get some kind of final conclusion. Anyone care to have a go about the science behind it?


Second idea...we're still looking for the softest light. We say we work with those imagined perfect diffusion distances...although maybe they'd change for this example. But now we have a 216 Full White Diffusion and a 252 1/8th White Diffusion. Which one should be the final and which the intermediate for the softest light?

Not my intention to bore. :)
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The Slider

CineTape

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Rig Wheels Passport

Aerial Filmworks

Wooden Camera

CineLab

rebotnix Technologies

FJS International, LLC

Media Blackout - Custom Cables and AKS

Abel Cine

Paralinx LLC

Willys Widgets

Metropolis Post

Tai Audio

Ritter Battery

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Glidecam