Rechner für Projektorhelligkeit & Foot-Lambert

How to use it: enter screen size, rated lumens, an estimated delivered-output percentage, screen gain and your comparison target. This keeps marketing output separate from the lumens assumed to reach the screen.

Formula. Foot-lamberts = delivered lumens x gain / screen area in square feet. Approximate cd/m² = fL x 3.426. Reverse rated lumens also accounts for the entered delivery percentage.

Example. A 2500-lumen projector modeled at 70% output delivers 1750 lumens before screen gain and area are applied.

The result above uses these exact values. This snapshot is included when the page is printed so the output can be checked against the original measurements.

Screen diagonal

120 in

Aspect width

16

Aspect height

9

Rated lumens

2500

Estimated delivered output

70 %

Screen gain

1

Target brightness

16 fL

Primary result: Estimated screen brightness: 41.0 fL.

• Measure from the datum or reference edge described by this tool, and do not mix inside, outside and centerline dimensions.
• Keep inputs in the displayed units and preserve more precision than the final cutting or purchasing tolerance requires.
• When the result is close to a limit, verify it with a test piece, field measurement, manufacturer drawing or qualified project professional.

This is an idealized uniform-screen estimate. Calibration mode, zoom, lamp/laser age, optical losses, screen directionality, ambient light, contrast and measurement position affect the real image. Measure the installed system when brightness matters.