Quote Originally Posted by SourceChild View Post
Hey Peter,
Something else you can try would be a different projection screen medium. Part of the reason the image looks perceptibly darker to the edges is that your eyes are not directly on axis with the lens of the projector. Some screens account for this and others do not. Typically the ones that do have characteristics similar to road signs where no matter where you're shooting from, the image always seems to reflect back toward you.
perceptibly darker to the edges
this is not an explanation for this-

this effect is fundamental to the nature of projection coupled with reflection of light off diffuse surfaces-

projection surfaces dont come close to ever giving a perfect diffuse reflection of a surface- with even reflected light in all directions-

this is a very complex subject - and nothing to do with projectors themselves and all about material properties.

road signs are a red herring - they would make a terrible projection surface- - why dont you try one?
then try a piece of white laser printer paper?
which one makes the best surface?

http://en.wikipedia.org/wiki/Diffuse_reflection
http://en.wikipedia.org/wiki/Specular_reflection