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What is Lux?
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. When choosing a camera to operate in ambient lighting conditions, this can often be a relatively difficult specification to apply.
Light levels are normally measured in LUX. A Lux measurement is the measurement of light energy reaching a 1m² surface area per second.
It is wise to exercise caution when viewing specifications which quote Lux levels such as 0.0001 etc., as unless the camera incorporates integrated Infrared Leds (IR) or an external light source is available, the quality of an image captured at low lux levels is unlikely to be of much use.
Day/ Night Cameras overcome this problem by allowing the camera to record in colour under normal light and automatically switching to Black and White in low light environments. Some Day/Night Cameras are also Infra Red Sensitive, allowing for the use of integrated or separate Infra Red Lighting to increase the cameras range in low light and complete darkness. Whilst this is achieved electronically in some cameras, higher quality i-Lax cameras incorporate a mechanical cut filter which produces better quality operation under Infra Red Light.
During the day the amount of illumination reaching a scene depends on the time of day and atmospheric conditions. Direct sunlight produces the highest-contrast scene, allowing maximum identification of objects. On a cloudy or overcast day, less light is received by the objects in the scene, resulting in less contrast. To produce an optimum camera picture under the wide variation in light level (such as occurs when the sun is obscured by clouds), an automatic-iris camera system is required. The chart below provides an approximate LUX level under vaious lighting conditions.
|Lux & Low Lighting Chart|
Retail and Office
Very Dark Day
Main Road Lighting
Residential Street Lighting
0.5 - 3
Low Light Level Range
Lux x 0.0929 = Foot-candles