A:Answer To answer your question, I need to know if you're measuring screen width from side to side or diagonally (from one corner to the opposite corner.) Assuming width is from left side to right side, the projector set-back is found by multiplying the screen width by the throw ratio of the projector. This projector has a throw ratio of 1.35 to 1.64, So to produce a picture 120" wide (10 feet) the projector has to be 13.5 to 16.4 feet from the screen. On the other had, if you're screen measure is diagonal, you need to look at the width to height ratio to figure true screen width. As most video screens today are a 16:9 ratio, your magic number is 0.872. Multiply your diagonal screen width by that number, then multiply by the throw ratio: 10' x 0.872 x 1.35 = 11.7' minimum, 10' x 0.872 x 1.64 = 14.3' maximum. If you're using the older, original TV format ratio of 4:3. the magic number is 0.8 for a minimum and maximum distance of 10.8' to 13.1'.
