Footlamberts for Projectors: What and Why?

A footlambert (or foot-lambert) is a unit of luminance. It is used primarily in the projection industry to provide a value for luminance of images on a projection screen.

1 footlambert (fL) is equal to 3.43 candela per square meter (cd/m2).

When the footlambert value is known for a projection system (the projector and a screen), assumptions can be made about the clarity of images when viewed with varying ambient light levels in a room.

To calculate the footlamberts on a screen you need the following units:

• Projector Lumens
• Screen Gain
• Screen Width
• Screen Height

Use online calculators to get the footlambert total for your system and the recommended range for acceptable ambient light. Here are two web sites with calculators:

ProjectorScreen.com (scroll down this page to find the footlambert calculator)

ProjectorCentral.com