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Old Jan 7, 2011, 1:19 PM   #1
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Default poor man's diffuser

I'm getting ready to dig out my monstrous light box (that contains 12-200w CFLs) for an upcoming event. For whatever reason, I am still needing more light from it. Since the CFLs are already fairly diffuse, can I get by with a cheese cloth for a diffuser?
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Old Jan 7, 2011, 2:01 PM   #2
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Or, you can use a shower curtain.
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Old Jan 8, 2011, 12:05 AM   #3
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Hmmm, even a clear plastic would offer diffusion, increasing in softness as the opacity increases. Now I'm thinking about a clear sheet of acrylic, sanded starting at 2000 grit and working down to 100 grit until I can't make out an individual bulb...
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Old Jan 8, 2011, 7:54 AM   #4
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Originally Posted by iowa_jim View Post
Hmmm, even a clear plastic would offer diffusion, increasing in softness as the opacity increases. Now I'm thinking about a clear sheet of acrylic, sanded starting at 2000 grit and working down to 100 grit until I can't make out an individual bulb...
Or, a white nylon shower curtain. It would save you a lot of work. Make up a PVC frame and you can experiment with any sort of combination/color/pattern.
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Old Jan 12, 2011, 12:18 PM   #5
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The "job" of the diffusion material is to transmit directly received light, that is light from the bulbs which is perpendicular to the plane of the diffuser, and light arriving at more oblique angle, the light from the reflector, so that they appear equal. In effect this is making your soft box appear as a large, uniform light source.

Part this requirement can be accomplished if the diffuser material bounces part of the light that hits it back into the reflector to be returned again to the diffuser. Therefore I'd be inclined to think a white material such as the white shower curtain suggested above or the white polyester "cling free linging" fabric I used for my light tent might be more effective than any of the translucent material that have been suggested.

Frosted or ground glass or its plastic equivalents (your sanded acrylic) "hot spot" when used for rear projection screen. That is they white out in the center when viewed head on. Increasing the coarseness of the grind reduces the resolution but not the hot spoting. One report (http://forums.makezine.com/comments.php?DiscussionID=43) suggests that an effective rear projection screen can be built with two layers of wax paper layered at 90 degrees. See the discussion for construction details and methods. It may be that sanding both sides of an acylic panel might be more effective than one coarse side.

Here are some sources for rear projection screen material. Their products may not be budgetarily feasible but the descriptions/explanations may give you some ideas: http://www.rosebrand.com/product703/...on-Screen.aspx, http://www.ezscreen.com/esp.html, and http://www.projectorpeople.com/screens/surfaces.asp.

Finally, your local "big box" hardware store (Menards, Lowe's, Home Depot) was acrylic diffussion material in their ceiling tile department for use with in ceiling light fixtures. Idea, do you have one of those little 9 LED, plain round cylinder, three AAA battery flash lights? I'd stick that right behind the various diffusion tiles (or other diffusion materials) and pick the one that made those 9 LEDs look like a single source.

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Old Jan 16, 2011, 2:17 PM   #6
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Finally, your local "big box" hardware store (Menards, Lowe's, Home Depot) was acrylic diffussion material in their ceiling tile department for use with in ceiling light fixtures. Idea, do you have one of those little 9 LED, plain round cylinder, three AAA battery flash lights? I'd stick that right behind the various diffusion tiles (or other diffusion materials) and pick the one that made those 9 LEDs look like a single source.

A. C.
I've now looked at pre-made diffusion panels. A local store had 2'x4' panel by Plaskolite and using the LED flashlight test I suggested the Plaskolite Cracked Ice White pattern provided the most effective diffusion. I also found that the diffusion is not bi-directional, that is some panels worked best with the smooth side toward the light and some with the textured side toward the light and in either case whites were more effective than clear regardless of the pattern. The Cracked Ice White pattern worked best with the smooth side toward the light.

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Old Jan 17, 2011, 2:42 PM   #7
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I'll give that a try at my local box. Thanks for the help!
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