>Thanks for the explaination. I *think* I understand. So, if I see
>this right...it has a lot to do with the angle the light hits the
>mirror thereby determining how much gets pushed to the pentaprism?
>That would make sense to me I suppose.

That is part of what determines screen viewing brightness. The optical
design of the rear of the lens is also part of it. The aperture at the focal-length used on a variable perture zoom is part of it, too. And so,
too, is the design of the screen and viewfinder optics.

>Is there any corrrolation between viewscreen brightness and final neg
>sharpenss or are they independant of each other?

There is very little correlation.

>Thanks again for your time!

No problemo... David Ruether