Q: What is "Lux" for cameras?

A : LUX is defined as "Relative amount of light that will produce a viewable image." Cameras actually work in the opposite of the ratings of LUX. LUX is actually amount of light created where cameras are capturing light.

Below is a general reference of amount of light created in LUX ratings.
A few lux ratings for reference;
The sun - 100,000,
Sun with light cloud - 70,000,
Sun with heavy cloud - 20,000,
Home/office lighting - 100-1000,
Sunrise/sunset - 500,
Street Lighting - 1-10,
60 Wt. Bulb 10 ft. away - 10
Twilight - 4,
Full moon - 0.2,
Quarter moon - 0.02,
Overcast moon - 0.007,
Clear night sky - 0.001,
Average starlight - 0.0007,
Overcast night sky - 0.00005