The difference between backlight compensation BLC, strong light suppression HLC and wide dynamic range WDR
Positioning of the three
| Functions | Ideas | Typical Scenarios |
|---|---|---|
| BLC backlight compensation | Weighted metering of the specified area in the picture to suppress the bright background | People/objects are in front of strong light windows, but there is no need to see out of the window clearly |
| HLC strong light suppression | Directly suppress the highlighted areas in the screen | Interference from point light sources such as car lights and searchlights |
| WDR wide dynamic range | Multi-frame/double exposure synthesis, while retaining light and dark details | Need to see clearly inside and outside the window, indoors and outdoors at the same time |
Why can’t they be opened together
BLC and WDR are both mechanisms that "change the metering and synthesis strategy". If they are turned on at the same time, they will fight each other. It manifests as the picture flickering on and off, and the bright parts flickering. Most devices also don't allow simultaneous activation. HLC and WDR can generally coexist, but strong light suppression will weaken the detail retention of wide dynamic range in bright areas.
Select by scene
- Doorway, front desk: The background is a glass curtain wall or window, the focus is on seeing faces clearly - priority WDR.
- Underground garage entrance: Direct light from the car is the main interference - give priority to HLC, and add WDR if necessary.
- Night channel: When there is only partial fill light and the background is completely black, BLC can actually make the subject stand out more.
- No strong light source indoors: There is no need to turn on any of the three options. Turning them on will only increase noise and delay.
The cost of wide dynamic range
WDR is not free: multi-frame synthesis will add about 1 to 2 frames of delay, and moving objects may have slight ghosting; Turning on WDR under low illumination will significantly increase noise. Therefore, "turn it on during the day and turn it off at night" is a common practice. Some models support automatic switching based on time period or illumination, and it is recommended to enable it.