Let's say I have total projector placement flexibility to obtain a given screen size.

To get the best contrast ratio, would I want to place the projector as close to the screen as possible or as far away from the screen as possible?

Thanks!

Min zoom (PJ farthest from the screen) gives greatest CR but least brightness. Max zoom (PJ closest to the screen) gives worst CR but greatest brightness.

For an example of the differences, here's some readings from a cine4home review of the Infocus IN76. For those PJs with a greater throw range (ex. Panasonics) the differences will be even greater.

Infocus IN76
Maximum Zoom 800 lumens (Hi-mode) / 580 lumens(Eco mode) 1500:1
Minimum Zoom 690 lumens (Hi-mode) / 500 lumens (Eco mode) 1800:1

http://www.cine4home.com/reviews/projectors/InfocusIN76/IN76Review.htm