Diffusing materials

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.

 

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

 

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