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#1 Chayse Irvin

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Posted 24 March 2007 - 03:33 PM

How many stops does Muslin take the light down? I went to look in my harry box and coulden't find it.
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#2 Michael Nash

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Posted 24 March 2007 - 07:29 PM

The light loss from any diffusion material varies with the size of the illuminated diffusion and its distance between the light and the the subject. It's not a scrim; the muslin instead becomes the light source.

I would expect to lose maybe at least 2-3 stops, if you're trying to estimate how large a unit to put behind it to reach a desired light level.
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#3 Chayse Irvin

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Posted 26 March 2007 - 03:23 PM

The light loss from any diffusion material varies with the size of the illuminated diffusion and its distance between the light and the the subject. It's not a scrim; the muslin instead becomes the light source.

I would expect to lose maybe at least 2-3 stops, if you're trying to estimate how large a unit to put behind it to reach a desired light level.


I'm looking to estimate how large of unit and what the heaviest diffusion I can get away with would be. For my tests purposes I'm going to place several diffusions in the same situation and read which one takes off the most light at whatever distance. For example if you placed all different types of diffusion on the barn doors of a lamp and take a reading say... 8 feet away. 216 (-3 1/2 stops), light grid (-3 1/2 stops), full grid (-5 stops)? now my question is how much light would muslin takes off? I'm going to have to test it.
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#4 Michael Nash

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Posted 26 March 2007 - 06:46 PM

I understand what you're saying, but that kind of a test doesn't really emulate real-world conditions and wouldn't give you much useful information. Calculating exact stop loss is a bit of a moving target -- it changes so much with all the variables of a real setup that any "barn door test" figures you came up with would only confuse the issue.

It is useful to know the relative densities of various diffusion material, as a rough guide. But usually they're chosen for their diffusion properties more than for their transmission (until you get down to the really light stuff, where it may be more important to not cut the light too much). Because in addition to stop loss, there are the unique characteristics of the diffusion like how much hard light or double-shadow it creates, how directional or diffuse the transmitted light becomes, and so on.

If you want to use a heavier diffusion to get softer light, you often reach a point where additional density just cuts the light more, but doesn't soften it any more. You then have to step up to a larger surface area, or change your lighting setup (often by putting a less-dense diffusion a little bit in front of the diffused unit).

I like to experiment with different combinations of units and diffusion to get the look I want. For example, a Maxibrute through polysilk can give you a different type of spread, shadow, and falloff than a 10K fresnel through the same diffusion.
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#5 Chayse Irvin

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Posted 26 March 2007 - 07:34 PM

I understand what you're saying, but that kind of a test doesn't really emulate real-world conditions and wouldn't give you much useful information. Calculating exact stop loss is a bit of a moving target -- it changes so much with all the variables of a real setup that any "barn door test" figures you came up with would only confuse the issue.

It is useful to know the relative densities of various diffusion material, as a rough guide. But usually they're chosen for their diffusion properties more than for their transmission (until you get down to the really light stuff, where it may be more important to not cut the light too much). Because in addition to stop loss, there are the unique characteristics of the diffusion like how much hard light or double-shadow it creates, how directional or diffuse the transmitted light becomes, and so on.

If you want to use a heavier diffusion to get softer light, you often reach a point where additional density just cuts the light more, but doesn't soften it any more. You then have to step up to a larger surface area, or change your lighting setup (often by putting a less-dense diffusion a little bit in front of the diffused unit).

I like to experiment with different combinations of units and diffusion to get the look I want. For example, a Maxibrute through polysilk can give you a different type of spread, shadow, and falloff than a 10K fresnel through the same diffusion.


Aye. I see there are many variables. For my practical reasons I'm really starting to use more and more often double diffusion through 6x6 and 12x12 frames I'm trying to figure out what kind of light I?m going to need when doubling up Muslin because I?ve always used Full Grid, and I?m looking for a rough estimate of how much thicker Muslin is. I often get different looks with different lights but I've found that fresnel lenses have slight diffusion before the lens scatters the beam, but when I'm doubling heavy diffusion it really doesn't matter what kind of light it is, but how much you can get out of it. Maxi Brutes are usually my choice for night exteriors, and 2 Mini 9's rigged on an offset, with one mini9 above and another below the rig allowing me to cover the whole diffusion frame in tight spaces, are my current choice of fixture. But I?m really wondering if that would work with muslin because I hardly use it, but want to start experimenting. I'm also interested in throwing Muslin over kinos and such when I can get a light really close to the actor.
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#6 Michael Nash

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Posted 26 March 2007 - 09:45 PM

Ultimately you just have to try it out.

If you're concerned about the total stop loss with two frames of diffusion, you could use something lighter on the frame closest to the subject. Assuming frames of the same size, once the light has been softened by a heavy diffusion you don't always need as heavy a density on the second frame.
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