Diffusion Materials

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Diffusion Materials
by Ben Ferrer on Mar 13, 2008 at 10:41:24 pm

I need a help understanding the differences between China Silk, Artificial Silk, and Lightbox Diffusion materials.

I see in the Matthews catalog that the light loss varies by .2 and .6 stops, but the discriptions regarding the quality of light are vague. I need to know which of the three, or some other material, will give the softest transfer of light.

I plan on using this in a 12'x12' frame on a large sound stage; primarily as a key. The goal is to eliminate all traces of hard shadows.

My experience with most silks is that some direct light from the source passes through creating faint, but visible, hard shadows. I want the same quality of light that I get from my Chimera, but on a large scale.

What is the best material for this?

Thanks in advance.

-Ben

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Re: Diffusion Materials
by Bob Cole on Mar 16, 2008 at 6:44:51 pm

[Ben Ferrer] "The goal is to eliminate all traces of hard shadows."

Sure, the type of diffusion has an effect. But that has less impact than the size and positioning of the diffusion surface relative to the subject. A perfectly diffused source that is far away will be "harder" than a less-diffused source right on top of the subject.

If you don't want shadows, you're usually looking at wrapping the light around the subject, so perhaps you want to use several diffused sources from different directions. But if your 12x12' is right next to the camera, and close to the subject, the shadows will be trivial with any of those diffusion fabrics, as long as the light source covers the entire 12x12 frame.

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Re: Diffusion Materials
by Ben Ferrer on Mar 16, 2008 at 10:33:03 pm

Bob,

Thanks for the reply.

I should have been more clear about what I need.

What I'm trying to control is more subtle. The hard shadows I want to eliminate are the faint ones that result from the hard source light that passes through a material without being diffused. It's a small percentage, but some hard light still gets through a standard artificial silk. This isn't a question of flat lighting or wrap, but specifically about transmission. Which material(s) will only transmit the scattered rays and not "leak" any of the direct hard light from the source?

I'm hoping to learn about the differences between China Silk, and Lightbox Diffusion as compared to artificial silk.

Best,

-Ben

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Re: Diffusion Materials
by john sharaf on Mar 16, 2008 at 11:01:12 pm

Ben,

You are correct in your observation that some silks still allow a specular source resulting in harder shadows than others. This is definitely observable if you position yourself down light from the silk and look back into the light source; you can actually see it. Now if you use a heavier diffusion like a muslin you won't see the light source anymore and you'll have much less shadowing on your subject. In between are frames made of various degrees of white diffusion like Lee filter 250, 216, etc. On these diffusions you'll notice when you look into the light source that the whole frame of diffusion is evenly lit and there will be no specular. Of course the heavier the diffusion, the less transmission and you'll require a large lighting instrument to maintain the same amount of illumination.

JS

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Re: Diffusion Materials
by Todd Terry on Mar 17, 2008 at 12:11:23 am

Hi Ben...

I agree it can be a little bit confusing... you read the specs on all the rags but can never be sure just how much diffusion the various products offer. I'll admit I've bought one or two silks through the years only to find it wasn't exactly what I was expecting as far as transmission quality.

Your best bet would be to find someone who is using exactly what you want, or seeing if anything is available at a rental house... and seeing which exact silk that is.

I'd say your second best bet would be just to directly call Matthews... talk to Ed or one of the guys there, they will be happy to help you. If you describe exactly what you are trying to do and the particular lighting conditions and instruments you will be using, I bet they can instantly tell you what would be best.

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com

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Re: Diffusion Materials
by Ben Ferrer on Mar 17, 2008 at 9:37:19 pm

Todd and John,

Thanks for the advice. I spoke with Pam at Matthews today. She was only able to quote from the catalog and didn't have any personal experience using the materials herself. However, she is sending a swatchbook of materials to me which will be most helpful. I'll give an update on what I discover.

-Ben

Ben Ferrer
DP - SF Bay Area

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