what size screen, how bright, how far — the generic version.
what size screen, how bright, how far — the generic version.
presets are typical — your screen's spec sheet wins.
throw ratio comes from your lens spec — throw ÷ image width.
bdm = H × 2 × %eh · adm = H × 3438 ÷ vertical px (1 arcminute acuity)
fL = (lumens × gain) ÷ area ft² · throw = ratio × width · max viewing ≈ 6–8 × image height
assumes a front-projection matte screen and a projector actually hitting its rated lumens (they rarely do after year one). derate older lamps 30%.
set the aspect and any one dimension — width, height or diagonal — and the rest follow. throw ratio from the lens spec gives throw distance; lumens against image area and screen gain give on-screen brightness in foot-lamberts and nits, against a target for the room.
fL = (lumens × gain) ÷ area in ft². asking how bright should my projector be is really asking for the target: about 16 fL in a dark theatre, 50 fL in a lit worship room. the discas panel gives the farthest seat that can read your smallest element.
derate anything with hours on it — a lamp past its first year is easily 30% down on rated lumens. size for the light you will have in year three.