Are there significant brightness differences between Lexan XL10 and tempered glass? Or are both fairly, similiarly, optically clear? I'm wondering, since if we use a UV filter with the tempered glass, and the Lexan already has it, are we getting less light through the tempered glass solution?

It has been discussed please use search.

Will you been able to see a difference, maybe a very very little. The properties of XL10 do say it has better light transmission, but alas I'll take my tempered as it won't bow or possibly discolour over time.

Lexan says that it transmits light better, and you do not have to lose more light with a separate UV layer. I feel this is important, as brightness is the major disadvantage to LL pj's, and you need to save as much as possible wherever you can. Most report that the Lexan works ok as long as it has room to expand. Mine has been fine thus far, but I have only used it for about 4 hours.

I went from a single piece of Lexan to a single piece of tempered glass and didn't find the difference in light transmission to be anything noticeable. The Lexan kept melting and warping, causing distortions in my projected image that were completely eliminated by switching to the glass. Another benefit to the glass is the improved heat shielding.