Lux is a measure of the illuminance, or luminous flux, in an area. It can be used to indicate the amount of light given out by a particular light source, such as a light bulb in a room. Lux is typically measured at airports, for example in foggy conditions, to determine whether the light levels are high enough to allow planes to depart or land. It is also measured by councils to determine when to turn streetlights on and off.
Hanna offer a portable Lux meter that is ideal for measuring light levels.