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This topic describes the highlight compensation and wide dynamic range.
Nowadays, surveillance cameras pursue better HD video quality, which requires high device configuration and high image processing capabilities. To achieve better image quality, users also have higher requirements on surveillance cameras. In addition to night vision surveillance, do you understand Wide Dynamic Range (WDR)? Which is the most important function for checkpoint surveillance cameras: WDR or Highlight Compensation (HLC)? Can you distinguish them?
HLC' and WDR's sensitivity to light
Both HLC and WDR reflect cameras' sensitivity to light. WDR has become as common as night vision surveillance and is almost a standard configuration of surveillance devices. However, in terms of application and principle, there are many differences between WDR and HLC. Simply, a WDR surveillance camera can handle the impact of complex light conditions on images. However, it is not powerful enough to take snapshots of vehicle license plates at night.
Processing of subjects with light changes
The two different surveillance technologies are easy to confuse during their usage. In principle, the difference between the two technologies is obvious. HLC is to suppress the light source and better capture the subject in front of the highlight source. That is, the subject can be captured in a strong backlight environment. WDR is used when there is a strong contrast between bright and dark areas and can capture the subject while retaining the background.
Surveillance cameras with the two different technologies have a very similar approach to light processing. Both HLC and WDR use the backlight compensation (BLC) technology to better capture the subject or weaken the light contrast. HLC is to re-specify a metering area on the image and ensure appropriate exposure with dedicated metering to avoid casting shadows on the dark part. WDR is to split a video image into several areas and separately expose the areas.
In actual application, HLC is more suitable for road surveillance to identify license plate numbers by reducing the headlight halo. Generally, HLC can achieve better effect when working with white LED lights, such as at high-speed toll stations and crossroads. WDR is more suitable for underground parking lots or tunnels, where the indoor and outdoor light changes noticeably.
Effect comparison of WDR and HLC
Comparison of surveillance cameras that support HLC
The following figures show the effects before and after WDR is enabled. With WDR, the face and details of the subject are captured, and the background is not overexposed. Therefore, both the subject and background are retained.
Effect before WDR has been enabled
Effect after WDR has been enabled
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