This is defined as the luminous flux arriving at a surface that is perpendicular to it per unit area. The metric unit is the lumen m-2 or abbreviated to lux or lx.
In the British system this was defined as the lumen ft-2 or known as the foot candle or fc. 1 foot candle ~ 10.7639 lux
|Sunny day||10000 lux|
|Overcast day||1000 lux|
|Precision mechanical workshops, operating theatres||1000 lux|
|Supermarkets, workshops||750 lux|
|Normal office, library||500 lux|
|Warehouses, home, theatre||150 lux|
|Very dark day||100 lux|
|Full moon||0.1 lux|
|Quarter moon||0.01 lux|
|Overcast night||0.0001 lux|
For very detailed precision work the light level may need to be greater than 1500lux.
Photograph courtesy of industrial-needs.com
Note: It is very difficult to measure illuminance more accurately than ±10%.
- PCE Group Your advisor in measuring and weighing proficient.