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by Aditya

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There are hundreds of web sites with tips of building a DYI soft box or light tent, and it looks like people are using almost anything as the diffuser material, from white plastic bags to old t-shirts.

If I take a common household item that I might want to try to use as a diffuser, it is fairly easy to see how much it scatters light, how much it reflects light, etc. However, it is a lot more tricky to estimate how it affects the colours: if there is a slight colour cast, or if the diffuser blocks certain wavelengths. As we know, what looks like white to a human eye is not necessarily perfectly white...

Therefore I would like to know: which materials are good as diffusers and which materials should I avoid? Are there any useful rules of thumb in selecting the diffuser (besides experimenting with various materials)?

In particular, if I wanted to actually invest $5 in a diffuser, what kind of material should I buy? I would prefer a paper-like material, something that resembles wax paper or tracing paper.

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5 Answers 5

up vote 11 down vote accepted

The best diffuser I ever found was two-side-matte drafting film (either mylar or acetate). You get excellent diffusion and minimal light loss. The only problems with it are:

  • it burnishes, so you have to be careful with pressure and rubs when transporting or storing it; and

  • it's relatively stiff, so there are fewer options when constructing things out of it.

Another good material is frosted window film -- the sort of thing you'd use for privacy. You actually get a couple of different options here: frosted film gives very good, flat diffusion; while something with a micro-beaded texture gives a gradual radial fall-off with hotter highlights. This stuff is available by the foot at any home center.

If you want something that can be thrown casually into a bag without too many consequences, then a translucent white plastic shower curtain is a cheap option. It may be the last thing you want to have hanging in your bathroom, but it's good for photography.

I'd give muslins (beedsheets and so forth) a pass for most applications. Excellent diffusion, but they tend to block too much light. There's not a lot of point saving a couple of bucks on diffusers if you need to make up for it with tens or hundreds worth of more expensive lighting. That being said, it may be worth a trip to a fabric store to buy a couple of yards/metres of a white synthetic -- often they are woven of transparent yarns, and rely on the thread size/texture and weave density to give them the appearance of whiteness. Take a flashlight with you. You need to hit the right store at the right time of year, but you can often pick up something that's just as good as the expensive commercial products at a real bargain price in widths you can't get with paper products or drafting film. But if the fabric is in season or en vogue, it'll be on the pricey side.

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Thanks, drafting film sounds like a very good idea – and now I know what it is called! I had a vague recollection of seeing drafting film used in technical drawing more than 20 years ago, and I thought it might be a nice diffuser, but I had no idea what it is called (or what it is made of), which made googling or shopping a bit difficult... :) –  Jukka Suomela Feb 8 '11 at 0:53

White tracing paper, or white tissue paper (used for wrapping) works really well. I found that tracing paper was more expensive than white tissue paper, so I went with the later.

With regards to color cast, by using a greycard, and your camera's white balance setting, you can get around most basic color casts.

The downside to paper is that it's very easy to tear.

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I've tried using tissue paper, and it worked well, but was pretty easy to tear.

I later tried out a couple layers of plastic drop cloth. It works reasonable well, is durable, but doesn't diffuse the light quite as well as the paper.

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If you want to test out a diffuser, there's a pretty simple way to do so. Just hold it up to a light source, and see what color it is, and how much light penetrates the surface. If you see most of the light on the back side of the object, and it's mostly white, then you're good. If you want to use some color of light as a creative affect, you are also good. If you see something you don't like, then it might be a problem.

Also, consider things like the strength of the material, how easy is it to tear, etc.

Hope this helps!

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1  
"it's mostly white" is really the kicker. Our eyes perceive so many colors as white especially when looking at them like this. If you judge something as white, and then mix it with another shade of white from the ambient, you can end up with some "interesting" and difficult to get rid of shots. If you're just using flash as your light source, then its just a color temp change. –  rfusca Feb 8 '11 at 16:11
    
Yeah, but you could always use a gray card to correct for any non-whiteness that might appear, so... –  PearsonArtPhoto Feb 8 '11 at 16:31

Buy an old parachute off ebay, surplus store, or go to a fabric store and get some rayon, nylon, or ripstop nylon!

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