5 February 2012

Understanding Lux and Light Levels

Light levels or illuminance can seem complicated. The human eye can cope with a huge range of light levels, from less than 1 lux (lx) to nearly 10,000 lx. The graphic opposite looks at light levels in lux and what numbers relate to common environments such as reading desks or supermarket aisles.

Measurements in lux are relative to a particular surface, usually taken at the floor or a notional plane around desk height. This is because light diminishes as it gets further from its source and means that a light level measured at head height will be different from the level on the floor.

Illuminance (measured in lux) shouldn't be confused with Wattage, which is used to describe the power output of lamps and other light sources, or with daylight factors, which describe the percentage of light entering a building interior from the outside.