Efficient Diffusion material

Amonra · #1 06-24-2008, 01:28 AM

Im looking for some efficient diffusion material to be used in LED household lighting.

The fixtures use 3 x Cree XR-E's and are about 50mm in diameter. They originally had some optics but i removed them as the beam was too narrow. My problem is that with the XR-E's beam without optics is still too concentrated and not floody enough also there is a lot of glare and multiple shadows which i wish to remove.

I read on Cree's website that with some diffusion material the multiple shadows are removed and will produce a nice homogenous light output.

I have tried adding some frosted plastics but the light output drops significantly with them so i was wondering if there is some specialised high efficiency diffusion material i could use.

Your help will be greatly appreciated.

Thanks

Citivolus · #2 06-24-2008, 04:26 AM

Personally Roscolux Tough Rolux is on my list of diffusion materials to try, but it may not be rigid enough for your purposes unless you can lay it on top of the existing lens in the fixture.

Regards,
Eric

Flashlight Aficionado · #3 06-24-2008, 05:48 AM

98% Transmission rate with LDF coating and they go up to 72mm

UCL lens with LDF

Quote:

UCL® Lens
Our most popular lens. Water-white glass that has an anti-reflective coating on both sides. Transmission rates are about 99%.

Add LDF? (Light Diffusion Film)* LDF stands for "Light Diffusion Film." We take GE brand Lexan® that has a slight texture to it and, using an optical adhesive, apply it to one side of the lens. This results in more of a flood-like beam pattern. It will smooth out the worst beam. The overall light output is almost unchanged - it’s just spread out more. Be warned though, this coating will kill the throw of the light. Only add this coating if you like a really smooth beam and lots of side-spill. We recommend placing the LDF side of the lens toward the bulb for protection against scratching.

TONY M · #4 06-24-2008, 10:30 AM

As silly as it sounds I have used office(?) tape to diffuse flashlight beams for cycling. I don't know the name of the tape but it was the type that is not transparent unless very close to something.

I photographed the light by doing a ceiling bounce test before and after taping over the lens and there was virtually ZERO loss of light proving that it was very effective.

Led_Blind · #5 06-24-2008, 10:51 PM

Quote:

Originally Posted by TONY M

As silly as it sounds I have used office(?) tape to diffuse flashlight beams for cycling. I don't know the name of the tape but it was the type that is not transparent unless very close to something.

I photographed the light by doing a ceiling bounce test before and after taping over the lens and there was virtually ZERO loss of light proving that it was very effective.

you probably cannot see the 5-7%loss

but i have done the same on led replacement 12V spotlights. Works well and protects the optic.

Burgess · #6 06-24-2008, 11:48 PM

(former) CPF member, FastCar, did lots of testing and research.

He came up with a couple Excellent choices.

Try searching "Fastcar diffusion" for more info.

Hope this is helpful.
_

BIGIRON · #7 06-25-2008, 09:31 AM

I think 50mm is about 2 inches, so PDF screen protectors should work. IIRC the ones for the b&w screen work best. The tape is Scotch Matte or Satin transparent, also IIRC.

I've used both on a variety of lights with success.

Amonra · #8 06-25-2008, 04:03 PM

I went for the UCL with LDF which seems to be similar to what Fastcar was selling ( 5 layer ) although almost all of Fascar's threads seem to have been deleted.

I just hope it will be enough as these things dont come cheap ( i needed 16 pcs ) if it is not enough ill add some satin scotch tape or the pdf screen protectors.

BIGIRON · #9 06-25-2008, 04:51 PM

I think someone has used clear "Contact Paper" (like for lining kitchen shelves). Again, IIRC.

gunga · #10 06-25-2008, 06:04 PM

If you want FASTCAR's diffusion stuff, he still sells it on light-reviews.com/forum.

I use the 5 layer and 10 layer stuff. 10 layer is total flood, 5 layer smooths out the beam. There is a loss in throw (5 layer), I'm unsure there is much loss in output.

It's reasonably cheap so you could just try a bit out.

Amonra · #11 06-26-2008, 09:14 AM

at $2 a square inch it wont be very cheap as i need 64 sq inches.
mind you the UCL with LDF did not come cheaper but at least i got a lens too and i needed one anyway.
well see if it will do the job when they arrive

Citivolus · #12 06-26-2008, 11:41 AM

I'd be interested to see your results when it arrives.

Regards,
Eric

jeffosborne · #13 07-02-2008, 12:48 PM

I have found that artist's tracing paper, found at Blick Art Supplies and other art stores, does a great job. It's more like velum than paper, kind of a thin plastic feel to it.

Measuring with my trusty Minolta camera, I loose about 1/2 F-stop, or 25% by using it. That sounds like a lot, but that's what a diffuser does - scatters the light. So where my home-built photography light with 6 neutral-white Rebels normally has a 160 degree angle of dispersion, with the diffusing material it is much wider, thus diluting the foward light a bit.

Cheers,
Jeff

Amonra · #14 07-21-2008, 01:46 AM

I got the UCL's with LDF and they do not seem to drop the total output however they do not diffuse the light enough so i decided to sand the back side of the UCL with some sandpaper to turn the glass matt they are diffusing a little better and no light loss but still not quite up to my requirements.