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Diffusing materials

Discussion in 'Lighting' started by Richard, Dec 5, 2006.

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  1. Richard

    Richard Guest

    A light inside a closed box, either a LED or lamp. You don't always want
    to see the light source clearly, in fact you just want an even light
    emission from the box front.

    Assuming the light source is going to shine on the diffuser
    (backlighting the diffuser), can anyone please just suggest to me what I
    could use as a diffuser to put in front of a mood light I'm seeking to
    knock up?

    I can think of sheet plastic, but maybe you guys can suggest other
    things. Thanks.
     
  2. David Lee

    David Lee Guest

    Richard wrote...
    The answer's in the question - try Diffusion Materials! Specifically -
    Diffusion Material manufactured for theatrical lanterns such as
    www.rosco.com/us/filters/supergel.asp#Colors.

    Scroll down to the end of the list and request a Swatchbook since,
    unfortunately, you can't get any impression of the degree of diffusion from
    the on-line chart.

    However Frost (colourless) and Diffusion (coloured) are matte finished to
    diffuse the beam in all directions whereas Silk has a linear finish that
    diffuses in one direction only, across the sheet. Matte Silk (colourless)
    is a combination of both - giving a greater degree of diffusion in one
    direction. The various sorts of Frost all have varying degrees of
    diffusion.

    Price over here is typically 4.35 UK pounds for a sheet - 500mm x 610mm or
    62.30 UK pounds for a full roll - 610mm x 7.62m

    David
     
  3. TKM

    TKM Guest

    The electric sign industry uses diffuse white acrylic plastic (there are
    several grades and thicknesses) and the following rule-of-thumb: Space the
    light sources no further apart on center than 1.5 times the distance between
    the diffuser and the source.

    I know the above works for fluorescent and for frosted or clear inandescent
    light sources; but I haven't tried it with LEDs which are, of course,
    directional and have a relatively high brightness.

    As for the diffusing material, the trick, if you can't get acrylic sign
    plastic is to find a good diffuser that doesn't also absorb too much light
    or change the color of the light. Many kinds of plastics have good
    diffusion; but they are also likely to have high absorption.

    Terry McGowan
     
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