Diffusing light from an LED light board

I got one of those LED light board things you see on eBay to serve as a light box but it has some sort of black grid (picture 1) on it which can be seen through negatives when you place them on top of it. The holes for the grid are quite large in comparison to the negative's frame. This makes this light board impossible to use in combination with my digital cameras to digitize the negatives. When I place the styrofoam bag it shipped with over the light board to defuse the light it still shows through, albeit less so (picture 2, 3). Placing a sheet of blank white printer paper over the board eliminates the visible black and white pattern through the lighter portions of a negative (picture 4) but makes the light much flatter than if I hold the negative up to a light fixture (picture 5). Any suggestions for creating uniform light behind the negative without making it look as dull as when using paper?

You could try a frosted panel above the LED source, above it by at least a couple inches to reduce hot spots.

I used some thin sheets of a frosted material called DuraLar Matte which I purchased from an art supply shop. In my case, the DuraLar was elevated above the LED light panel by about 1/2 inch, and it took two sheets. If you start with <this link> and click through the next few images, you can see what I'm talking about.

runswithsizzers said:

I used some thin sheets of a frosted material called DuraLar Matte which I purchased from an art supply shop. In my case, the DuraLar was elevated above the LED light panel by about 1/2 inch, and it took two sheets. If you start with <this link> and click through the next few images, you can see what I'm talking about.

Click to expand...

That should work. I used an LED panel for an enlarger light source and I used diffusion material for movie lights. Used 2 layers also, and spaced the second one off about an inch with a picture frame. Works great.