What is a common measurement unit for brightness of projectors?

Lumens is a common measurement unit used to quantify the brightness of projectors. It specifically indicates the total amount of visible light emitted by a source in all directions, making it an essential metric in the audiovisual industry for determining how bright a projected image will appear in a given environment. Higher lumen ratings typically mean that the projector can produce brighter images, which is particularly important for presentations in well-lit rooms or environments where greater visibility is required.

Foot-candle and lux are both units that measure illuminance, referring to how much light falls on a surface, but they are not specific to projectors. A lux meter, while used to measure illuminance in lux, is not a unit of measurement itself but rather a tool used to measure that illuminance. Thus, lumens is the most relevant and widely recognized measure for projector brightness.