How to fix the backlight problem of surveillance cameras?

The basic condition of camera shooting is forward lighting, backlighting has always been a taboo in shooting, but in many cases we have to shoot in backlighting conditions. Backlit shooting refers to shooting when there is a light source behind the subject or the background is relatively bright. When backlit, compared with the brightness of the background, the object being photographed will appear darker, and it is easy to form shadows. Too much backlight will cause the subject to be underexposed.

For example, many times we need to take pictures of people standing in the window from the inside, or take pictures of the door from the store lobby. At this time, the subject is backlit, and the camera is exposed with reference to a brighter background, but the subject becomes darker. Therefore, it is difficult to take a clear picture.

Camera backlighting is a problem often encountered during the installation and commissioning of surveillance projects. Too much light at the door will easily cause the screen to become black. At this time, we will try to adjust the position of the camera installation, but more often, the camera position is not casual It can be adjusted and must be installed in the backlight environment. What should I do at this time?

Generally speaking, there are three main ways to solve the backlighting of the camera. One is to avoid direct sunlight when installing the camera; the second is to choose a camera with corresponding improvements, such as a wide dynamic camera or a backlight compensation camera; three can increase the illumination of the indoor light source. To reduce the contrast with outdoor light, let's analyze them one by one:

First, adjust the installation position of the entrance and exit cameras to avoid direct sunlight from the outside as much as possible, which can greatly improve the backlighting phenomenon at the entrance and exit. For example, a camera needs to be installed at the entrance of the bank to monitor the people entering and exiting. If we install the camera facing the entrance, we may encounter more serious backlighting, which will cause the monitoring screen to be blacked out, and the problem of shooting real objects is not clear. At this time, experienced engineers will flip the camera that monitors the entrance and exit, so that the lens of the camera is facing the person who walks out of the outlet. This is better than installing the camera against the entrance and exit, and can better solve the backlight problem.

That is to say, when installing the surveillance camera, we need to solve the problem of the installation location. Try to avoid installing the camera in a backlit position. The most important thing is to look at the effect and the quality of the object.

Second, by selecting cameras with corresponding functions, the backlighting phenomenon is improved. There are two kinds of cameras in the security camera that can solve the problem of backlighting of the camera, one is a camera with backlight compensation function, and the other is a wide dynamic camera.

Backlight compensation, also known as backlight compensation, divides the picture into several different areas, and each area is exposed separately. In some applications, the field of view may contain a very bright area, and the contained subject is surrounded by the bright field, the picture is dim and no layers. At this time, because the signal level detected by AGC is not low, the gain of the amplifier is very low, and the brightness of the main body of the picture cannot be improved. When backlight compensation is introduced, the camera detects only a sub-region of the entire field of view. The average signal level in this area determines the operating point of the AGC circuit. Because the average level of the sub-region is very low, the AGC amplifier will have a higher gain, which will increase the amplitude of the output signal, thereby making the main picture on the monitor clear, greatly reducing the subjective brightness difference between the background picture and the main picture. The visibility of the field of view is improved. Although backlight compensation improves the brightness of the subject, the image quality is more or less deteriorated.