Applies to: All Reolink cameras

Description of the phenomenon: The camera can't see the license plate at night at all. The license plate at night turns into a white sequin or the license plate is overexposed in infrared mode.

Cause: The coatings used in license plates, traffic sign plates, and special work clothes all contain retro reflective materials. The characteristic of retro reflectivity is that when light is irradiated, the reflected light will be reflected toward the light source from the opposite direction close to the incident light. This is to clearly identify people and objects with retro reflective materials in the distance at night or when the vision is poor, which plays a major role in ensuring traffic safety and other fields.

Camera night monitoring mainly relies on the diffuse reflection of infrared light / white light from the object. After turning on the infrared light / white light, the infrared light / white light will irradiate the license plate, and it will be directly reflected from the license plate back to the lens, causing the license plate to appear as white sequins in the output image.

Note: This is a normal phenomenon, and all cameras will have this situation under night vision when the built-in infrared lights are turned on.

Solution:  After understanding the principle of retro reflective materials, we know that if you want to see the license plate clearly at night, the camera cannot turn on the infrared light at night. The usual practice is to install supplementary lights in other locations and force the camera in day mode.

For example, at the entrance and exit of a parking lot, install a white light fill light near the camera, and set the camera light to normally off, so that the license plate can be clearly seen.

Note: For the battery-powered camera, it's really not suggested being used to recognize the license plate since it is fixed lens and the PIR sensor needs about 0.8-1 second to wake up. If the car is moving too fast, the camera will not able to catch the license plate at all.