Lux
Lux was a unit of light illumination  equal to one lumen per square meter.

The Beacon of Kahless was capable of producing "massive photonic activity", producing an output of over 1 billion lumens per square meter. When the  was present in 2256, when the beacon was lit, the level of output it produced overloaded the ship's optical sensors, and was even too much for the plasmatic filters at operating at 100%. ()

While Data was dating Jenna D'Sora in 2367, and he welcomed her home to her quarters, he requested to the computer to "decrease illumination level by one third standard lux", before inviting her to sit with him on the sofa. ()

See also 
 Candles per square inch

External link 
 
Physics
Measurements