Screen gain

A matte white screen with gain 1.0 scatters light evenly in every direction. A gain screen concentrates more of it back along the projection axis, so seats near the centre see a brighter image and seats at the sides see less. The measure of that trade is the half-gain angle: how far off-axis you can move before brightness halves.

Gain is not free light. It redistributes what the projector delivers, which is why a high-gain screen can look superb from the centre and uneven from row A on the aisle. It matters most when checking screen luminance against the standard; the screen brightness calculator takes gain as an input.

Cinema screens are perforated so the loudspeakers behind them can be heard. UNIC’s handbook gives the figures: total open area of 4–5% of the screen for good sound transmission, with standard holes of 0.9–1.1 mm. Smaller "micro" perforations of 0.4–0.8 mm avoid the moiré patterns that standard holes can cause with high-resolution images. The space behind the screen for speakers should be at least 1,200 mm deep as a rule of thumb, or 1,000 mm if the last row is less than about 15 m from the screen.

Choosing a screen is therefore three decisions at once: gain for the room's width and any 3D system, perforation for the sound and the projector's resolution, and size for the room. Pair this page with cinema masking, the B-chain and the screen size calculator. Screen makers are listed in the supplier directory.