vga refresh rates on multiple monitors can interfere-
sometimes it works sometimes it doesnt.
60Hz isnt exactly 60Hz 75Hz isnt 75Hz.
at 1280x1024 its 59.98 and 1024x768 its 60.02 - things like this- at different resolutions the refresh is different
you set one screen to one resolution and the other to another - and the real refresh rates cannot be handled very well.
you have to test.
its much better on intel machines. but not good on older g5's
'edge' blending isnt just a computer thing - it can be the projector angle, the projector brightnesses, color temperature, angle of incidence, screen gain. all sorts of things.
projecting a image onto a screen - has falloff to the edges because the light has travelled further, and light falloffs is 1/(distance squared )