Light levels are measured in lux, and are generally defined as follows:
| Direct sunlight | 100,000 - 130,000 lux |
| Full daylight, indirect sunlight | 10,000 - 20,000 lux |
| Overcast day | 1,000 lux |
| Indoor office | 200 - 400 lux |
| Very dark day | 100 lux |
| Twilight | 10 lux |
| Deep twilight | 1 lux |
| Full moon | 0.1 lux |
| Quarter moon | 0.01 lux |
| Moonless clear night sky | 0.001 lux |
| Moonless overcast night sky | 0.0001 lux |
As well as the ability to handle various fixed lighting levels, a low-light network camera normally needs to handle changes (sometimes quite rapid changes) in lighting levels, eg an external camera needs to handle both bright sunshine and twilight. This can either be handled electronically (AES = Automatic Exposure System), or by an auto-iris lens, generally Direct Drive. A direct-drive, auto-iris lens changes the aperture of the lens to suit a wide range of lighting conditions and is recommended for environments where the lighting levels change considerably, particularly outdoors. We have a range of low-light IP cameras.
