Diffusion filter - what do I need ?

I've got a Maxabeam, Xenon searchlight. As you might know narrow beam is nice but wide beam has a big dark hole where no lights gets to. I would like to close this gap.

And where else to ask for suggestions then the photo-enthusiastics!

There is 100+35USD diffusion lens available but like to find me something cheaper.
Already have a snap-on bezel to fit a new window in, after I cut it to size dia. 125mm(5'').
So actually what I look for is material that gently diffuses and is heat resistant.

I've tested with an BFL 150mm aspheric lens, and with an acryl sheet fresnel 3D-lens, worked pretty good, wide beam with bright spot in the middle.
Found the aspheric a little to clear, showing impuritys, widening the spot but not blurring/blending.
The acyl fresnel wrinkled within 10 minutes due to the heat.( I found American DJ equipment sells cheap Diffusion material voor Led Par lights, but its not heat resisitant. Great voor torches probably)

Any one experience with glass fresnel lens on spot light? For example Strand, Auer, Arri lights.
Another good bet is some crystaline shaped surface that scatters the light all sides. ( Frosted fresnel is actually doing both isn't it? )

Got closer.

I've heard the original diffuser is opaque material, probably a plastic.

Received a sample Lee-filter from a most helpful Ebay seller. Widely used polyester sheets that are used to colorize and diffuse light in theaters. Pretty convincing !
I've used the protective window that clips-on, with the foil on the hot side and it held out without problem. So much more useful beam for closer up work.



One more thing I want to try, is etched glass.

Hi there. I built a tri of lights for a friend that does repairs on motorcycles, for him and staff. He wanted a high output light but yet to have a blanket effect of light. From the CPF Market place I purchsed diffusion film. I lined the inside surface of the lens . Behind this difustion film sits a XM-L 600LM LED. Casts a smooth flood of light. Will work well for inspection of parts, but they are quite impressive outdoors as well. Just to share.

This total cost less then 3 bucks. Worth a try !

Lee 216 Diffusion.
There will be a sample in your swatch book.

Like this:

http://www.filmtools.com/31-lee-s216.html