Understand Lux (Light sensitivity)

An IP surveillance camera’s light sensitivity is often specified in terms of lux, which corresponds to a level of illuminance in which a camera produces an acceptable image. The lower the lux specification, the better light sensitivity the camera has. Normally, at least 200 lux is needed to illuminate an object so that a good quality image can be obtained. In general, the more light on the subject, the better the image. With too little light, focusing will be difficult and the image will be noisy and/or dark. To capture good quality images in low light or dark conditions, a day and night camera that takes advantage of near-infrared light is required.

Different light conditions offer different illuminance. Many natural scenes have fairly complex illumination, with both shadows and highlights that give different lux readings in different parts of a scene. It is important, therefore, to keep in mind that one lux reading does not indicate the light condition for a scene as a whole.

Examples of different levels of illuminance

100,000 lux……..Strong sunlight

10,000 lux …….. Full daylight

500 lux ………… Office light

100 lux …………Poorly lit room

Many manufacturers specify the minimum level of illumination needed for an IP surveillance camera to produce an acceptable image. While such specifications are helpful in making light sensitivity comparisons for cameras produced by the same manufacturer, it may not be helpful to use such numbers to compare cameras from different manufacturers. This is because different manufacturers use different methods and have different criteria for what is an acceptable image.

To properly compare the low light performance of two different cameras, the cameras should be placed side by side and be viewing a moving object in low light.