Node Tree for Blenders compositor to simulate an old non-autofocus SLR viewfinder focusing screen

My old Pentax MX SLR was the reference. The compositing in Blender 2.6 is not perfect (can never be perfect) but it is very close to the real viewfinder.
viewfinder_final.blend 3.8 MB incl. all Images (29. Jan. 2012)
Node setup info screenshot