Managing Bright Scenes Using Back Light Compensation and Wide Dynamic Range
Backlight compensation and wide dynamic range are two modern technologies that allow cameras to produce better images in scenes that have bright and dark areas. The difference between the two technologies are discussed and shown in this article.
Backlight Compensation (BLC)
Backlight as its name implies refers to light behind an object of interest. An example of a scene with backlight is an open door behind a dark hallway. When viewed using a regular camera, a person at the door will appear silhoutted. This is because cameras automatically try to balance amount of light in a scene to keep them within acceptable levels. To overcome this limitation, a camera must have backlight compensation (BLC).
Backlight compensation works on the assumption that light levels should be optimized for the objects in focus. Using advanced camera circuitry, extremely high light levels are selectively shutdown while maintaining light for objects being observed. An example of BLC in action is shown below. The left image shows the image when BLC is turned off while the right one shows how the images looks when it is turned on.
Highlight Suppression BLC (HSBLC)
Highlight suppresion BLC is a type of BLC that is suitable for extremely strong light. It is specially suitable for detecting the plate of an incoming car with headlights turned on.
Wide Dynamic Range (WDR)
Dynamic range refers to the ability of a camera's chip to read and convert light information. The wider a cameras dynamic range, the better it can deal with scenes that have a large difference in foreground and background levels. Special chipsets have been developed to handle these kind of monitoring challenges. One of these is called the Pixim chipset. An example of WDR in action is shown below. The left image shows the image when WDR is turned off and the right shows how it looks when WDR is turned on.
BLC vs WDR
At first it might seem that there is no practical difference between BLC and WDR. In some scenes however, WDR produces better images that BLC. The video below shows an example.
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