Last night we were able to do a test with actual rear projection fabric taped to the rear of the front window. It looked great. I took some video but they really don’t do justice to how much nicer it was. There is only one pane of glass with the fabric on it in all the shots. Usually it is easy to see, if not look for the blue tape holding it up.
Viewing from the front you can see that the film evens out the bright spots although the image looks a little dimmer over all. It is still bright enough to read 8 inch type from the road. You might also notice the bouncing off the back mullions is minimized.
The difference is much more apparent at steeper viewing angles. With the film you can see read the sign from the stoplight even during the day. At night it is more pronounced.
From the inside during the day you can see this “cheaper” fabric is actually quite opaque but it does show the projection decently even in near full light. At night in the hallway you can see that with the fabric we have the option of showing colors and lighter backgrounds that were not options before.
Outside the screens is more apparent when we use a large field of white but also our pedestrian audience should be able to read the signage much better.
There was still some concern about how opaque the fabric we tested was.
**Update**
I did some looking into a local manufacturer and found out 3M does make something that looks nice. In theory anyway.
The Vikuiti product line has rear projection screen material that looks pretty heavy duty but there is also a wide array of Light enhancing films but according to their online info it hasn’t been used for this type of application yet.