Lux Levels

The human eye is limited to a visible spectrum of light. The photographic industry uses the metric Light Level "Lux" unit to indicate the measurement of the amount of light available in a given area. Foot Candles (FTCD) are rarely used, but are provided in the chart below for the sake of completeness.

Direct sunlight produces the highest-contrast scene, allowing easy identification of objects in the monitored zone. Less light is available on a cloudy or overcast day, resulting in less contrast, and that means it can be harder to identify objects in the scene, especially if they are moving. For outdoor surveillance, even under the best conditions light levels will vary throughout the day (clouds, fog, etc.). To produce the best picture under the widest variety of light levels purchase a camera with an auto-iris lens. Wide variety of auto-iris lens equipped cameras are available, and auto-iris lenses for full-size box cameras that have interchangeable lenses.

Infrared cameras that can pick up images in total darkness as long as a sufficient amount of infrared light are also available.