The difference between a normal camera and a night vision camera
With a normal camera, realistic colours and bright colours can be achieved by "adding a filter". The function of the filter is to filter out infrared light.
With night vision cameras, however, the function of the infra-red light is to add infra-red rays that pass through the lens to the image sensor, thus allowing the image to be imaged in the dark. In a night vision camera, therefore, the filter and the IR fill light are an oxymoron.
In order to achieve both the filtering of some stray light and the release of infra-red light, the night vision camera adopts a type of filter called "day and night filter", which must be able to release infra-red light in one step of the wavelength band, thus allowing infra-red light to pass through at night. But in the daytime, because of this function, the unwanted stray light is allowed to pass through, so the daytime colour is rather white and the colour brilliance is poor.
