How Captured a Clear Image in The Environment with Very Poor Light Conditions

Surveillance cameras demand captured clear picture in very poor light conditions at night, or no light environments. In the camera's indicators, we often can see the item: low illumination level .

1, the concept of illumination level

Illuminance is a unit to measure the sensitivity of the camera, represent by unit:Lux, that is to say, How dark lighting conditions the camera can capture the image. Indicating the lower the value, a lower light conditions the camera can take images. We know that the camera generated video signal by a nominal value of 1v, the standard value is 700mv, such as using the lens with aperture of F1.2, when the scene's illuminance values being photographed is 0.02Lux, the camera outputs a video signal amplitude is 33%-50% of the standard value of 700mv, when the lowest illumination lever for this camera is 0.02Lux/F1.2. Test the value of the illumination level should be noted that the size of the lens aperture, the smaller the F value, the bigger the aperture, the lower illumination need. The illumination values are different for different aperture.

2, The program to achieve low-light videography

We know that CCD camera can be divided into color and black/white cameras, the lowest illumination of ordinary cameras is in the table below.


The lowest illumination level of common cameras

The wave length range of visible light is 380nm ~ 780nm, wavelength of visible light is divided into red, orange, yellow, green, cyan, blue, purple from long to short, wavelength shorter than purple's wavelengths is known as UV, longer than red light is called infrared light. there is a layer of transparent electrode can absorb UV in the surface of CCD sensor, the CCD can not accept UV. Common color CCD camera chip have red, green and blue color filters, so color camera can not feel the infrared light . While the ordinary black/white CCD camera spectral range is very wide, not only can feel the visible light, but can feel the infrared light.

Based on the above principle, in the environment light conditions are very poor , engineers have often taken the following programs to get the clear images.

(1) general low illumination black and white CCD camera + IR Light

Install infrared light radiation "light" in monitoring site, generate infrared light ordinary camera can capture while the human eye can not see, can achieve night shooting through the black and white CCD camera.

(2) color to black and white camera + IR Light

The color to black and white video cameras means it is a color camera in the day, in the poor lighting conditions at night time, the use of the characteristics black and white images have a high sensitivity to the infrared , automatically switch to black and white mode, shooting in conjunction with infrared. Low-light cameras must be met to the lowest illumination the infrared light support.

(3) IR Illumination Color Camera

Infrared sensitivity of infrared low-light color camera is 4 times higher than the average the common camera, you can work at zero illumination (0Lux).

(4) low-speed shutter camera

Low-speed shutter camera also known as the cumulative picture camera, via store continuous multi-frame (up to 128 ) blurred picture due to insufficient light in computer memory, to build up a clear picture, with the help of SLOWSHUTTER technology to achieve shooting under 0.008LUX/F1 .2 illumination. This low-light video camera apply to museum, night observation of biological activity at night, the military coastline monitoring prohibit red, UV damaged.

(5) ultra-low-light cameras

Ultra-low-light camera use EXVIEWHAD technology to enhanced sensitivity greatly, its color illumination is up to 0.05LUX, black and white is up to 0.003-0.001LUX. When equipped special infrared devices, can get high-resolution black and white images, to achieve 0Lux shooting.