As promised I have some of my experimenting photos to share. I originally started this idea thinking it would be a smaller format 24" x 36" entrance marque, and have since decided that going with the flexibility of a larger poster format would be best.
The photos below are to show the "diffusor qualities" of different materials (this was with cheaper readily available 24 x 36 fluorescent light lenses). Keep in mind that many poster boxes utilize the more diffuse florescent lighting, which is very good but, requires more depth and 115volts. I want low profile and low voltage, therefore the LED strip light route. Seems getting good diffusion from the small high intensity LED bulbs is the bigger challenge.
Here is my test layout:
Here's the 3 materials I have checked out:
1) the far left is the thin cheap prismatic lens sheets that go into a fluorescent fixture
2) the far right is a similar thin sheet called cracked ice or crackle
3) the one in the center is what I will likely use, it is a piece of 1/8" white acryllic
And a few comparisons, in a dark room, with no flash.
Here's #1 the sample on the left - the thin prismatic lens material :
Here's #2, the one from the far right, "cracked ice":
And #3, the one I will be going with a thicker (1/8") white acrylic panel:
And one more; with the inside edges of the sidewalls were covered with shiny aluminum tape