Illuminance is a measure of how much luminous flux is spread over a given area. One can think of luminous flux (measured in lumens) as a measure of the total “amount” of visible light present, and the illuminance as a measure of the intensity of illumination on a surface.

A given amount of light will illuminate a surface more dimly if it is spread over a larger area, so illuminance is inversely proportional to area.

When a Camera Specification refers to Lux level, it is an indication of the lowest light level at which the camera will produce adequate image capture.

It is best to exercise caution when viewing specifications that quote operational Lux levels as low as 0.0001, as (unless the camera incorporates integrated Infrared LEDs or an external light source is available) the quality of an image captured at such a low lux levels is unlikely to be of any use.

Examples
Illuminance	Surfaces Illuminated By:
0.0001 lux	Moonless, overcast night sky (starlight)
0.002 lux	Moonless clear night sky with nightglow
0.27?1.0 lux	Full moon on a clear night
3.4 lux	Dark limit of civil twilight under a clear sky
10?40 lux	Total starlight
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
10,000 — 25,000 lux	Full daylight (not direct sun)
32,000 — 130,000 lux	Direct sunlight