Examples of the Illuminance
Here are some examples of the illuminance provided under various conditions:
Illuminance Surfaces illuminated by:
0.0001 lux Moonless, overcast night sky (starlight)
0.002 lux Moonless clear night sky with airglow
0.27–1.0 lux Full moon on a clear night
3.4 lux Dark limit of civil twilight under a clear sky
50 lux Family living room lights
80 lux Office building hallway/toilet lighting
100 lux Very dark overcast day
320–500 lux Office lighting
400 lux Sunrise or sunset on a clear day.
1000 lux Overcast day; typical TV studio lighting
10000–25000 lux Full daylight (not direct sun)
32000–100000 lux Direct sunlight
The illuminance provided by a light source, on a surface perpendicular to the direction to the source, is a measure of the strength of that source as perceived from that location. For instance, a star of apparent magnitude 0 provides 2.08 microlux at the earth’s surface. A barely perceptible magnitude 6 star provides 8 nanolux. The unobscured sun provides an illumination of up to 100 kilolux on the Earth’s surface, the exact value depending on time of year and atmospheric conditions. This direct normal illuminance is related to the solar illuminance constant Esc, equal to 128000 lux (see Sunlight).