Magnitudes and units
Amount of light emitted by a light source in all directions.
LUMEN ( Lm )
The luminous flux per unit area. (Density of light on a given surface)
LUX ( Lm/m² )
Part of the flux emitted by a light source in a direction given by the solid angle containing it.
CANDELA ( Cd )
Luminous intensity emitted in a given by a luminous or illuminated surface direction. (effect of “brightness” that a surface produces on the eye)
candela per square meter ( Cd/m² )
The main difference between Lumen and Lux is that Lux uses a surface as reference. This means that Lux uses a surface to distribute the light flow and Lumen do not use any reference. For example, if we concentrate 1000 Lm in a squared metre, we are lighting the surface with 1000 lux, but if we concentrate also 1000 Lm in a surface of 10 squared metres, we are only lighting this surface with 100 lux.
This means that the lumens of a lamp depends on the surface you want to light and the level of light you need.
|50 Lux||Sala de una vivienda familiar||20 m²||1.000 Lm|
|80 Lux||Pasillo/cuarto de baño||6 m²||480 Lm|
|400 Lux||Oficina bien iluminada||60 m²||24.000 Lm|