wich type of screen is the best for optoma hd72i?

Question

mat white or grey? and the gain? 0.9-1.00-1.2?

Answer 1

Here is the core of the screen recommendation section from the ProjectorReviews.com review of the HD72 (See link for the whole review):

"As a result, I would tend to recommend a high contrast gray surface for the HD72 if your screen isn't really large. Definitely for 100" diagonal or less. Myself, I'd probably stay with that recommendation to 110" or maybe even a little larger. Consider such screens as Stewart's Firehawk or their darker Grayhawk (which will really lower black levels), Da-lite's Cinema Vision or HC Cinema Vision, Carada's High Contrast Grey"