HP digital mp3130 Manual Do Utilizador

If you do not want to use the distance table, you can use the following equations to 
help determine where to install the projector relative to the screen.

distance from lens to screen = A × width of screen 

minimum and maximum distance from screen = B

width of screen = 0.8 × diagonal of screen (for 4:3 screen)

projector lens below bottom of screen = C × width of screen (for 4:3 screen)

A = 1.67 to 2.00

B = 1.2 to 12 m (4 to 40 ft)

C = 0.21 to 0.45