Projector Brightness Calculator

Work out the lumens a projector needs for the screen size, the room light and what the audience is watching.

Measure at the screen with the room set up as it will be used. A light meter, or a phone app for a rough figure, gives it.

Results

Screen area: 3.52 m²

Contrast target: 15:1

Light needed on the screen: 2,100 lux

Projector brightness: at least 7,383 lumens

With the ageing allowance: 8,859 lumens

Contrast targets are the four ANSI/INFOCOMM 3M-2011 viewing categories. The sum assumes the projector's own black level is small next to the room light. An ambient-light-rejecting screen lowers the brightness you need.

How it works

System contrast is the light from a white image plus the room light, divided by the room light alone. To reach a target ratio the projector must add (ratio - 1) x the room light, in lux, on the screen, and lumens are that lux x the screen area in square metres. The targets are the ANSI/INFOCOMM 3M-2011 categories: 7:1, 15:1, 50:1 and 80:1.

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