Video and displays
ANSI lumens
A standardized projector brightness rating averaged from nine points on a white test pattern, far more comparable than marketing lumens.
ANSI lumens follow a defined procedure: project full white, measure illuminance at nine points in a grid, average them, and multiply by screen area. Because the method controls for hot spots and lens fall-off, two projectors rated this way can actually be compared.
Unqualified 'lumens', 'LED lumens', or 'light source lumens' are measured differently and often run two to three times higher for the same unit. Brightness also drops in accurate picture modes and as lamps age.
A dark-room rule of thumb is 300 to 500 ANSI lumens per square meter of screen at unity gain, close to the 16 fL SMPTE target. A 100 inch 16:9 screen (about 2.8 sq m) wants roughly 1,000 to 1,500 calibrated lumens.
Related terms