A lamp produces a certain amount of light, measured in lumens. This light falls on surfaces with a density that is measured in footcandles or lux. A person looking at the scene sees different areas of his visual field in terms of levels of brightness, or luminance.
“lux” is a unit that indicates the density of light that falls on a surface. This is what light meters measure.

For example:

• average indoor lighting ranges from 100 to 1,000 lux,
• and average outdoor sunlight is about 50,000 lux.
• Direct solar radiation is about 100 000 lux.

The general term for lux is “illuminance.” This general term is sometimes used by lighting engineers, but the units of lux are more commonly used.

Light intensity in workplaces must fulfill minimum values and have to be checked regularly. Using software, a site list can be stored and individual luminous intensity values can be connected to form a curve. This light profile provides information on the uniformity of the lighting.