What Does Lux (lx) Mean?
Lux (lx) is the International System of Units (SI) derived unit that describes the measurement of illuminance, the total luminous incident on a surface as described in photometry. Lux means lumens per square meter (lm/m2 or cd sr m-2) and is colloquially referred to as brightness, which is then often confused with luminance. Both are similar, as they are both a measure of light, but lux takes into consideration the area while lumen does not.
Techopedia Explains Lux (lx)
Lux is a unit of measurement for light output in a given area (generally in square meters), or simply referred to as light intensity. This is a very appropriate unit for measuring the brightness of a beam of light where light is concentrated in a smaller area such as those in lighthouses, searchlights or flashlights. If the light is concentrated in a small area, one would perceive this as bright, but if the same amount is spread over a wide area then it is seen as dim. In this context, a searchlight with a beam concentrated in a small area that is perceived to be very bright and can travel long distances is considered as high lux, while a low-lux device would have light that is perceived to travel shorter distances but have a larger footprint. Even though both devices might be emitting the same amount of light, the beam is perceived to be brighter because it is more concentrated.
