Why should I adjust the white balance of the camera? When does the camera use the gain function?

The human brain can detect and more like this color change, so whether it is in the sun, cloudy days, indoor burning light or fluorescence. People still see the same white objects. But as far as cameras are concerned, the "white" produced by different light sources is still different in color, some contain light blue, and some contain yellow or red. In order to approach human vision, the camera must imitate the human brain and adjust the color according to the light, so as to present the white seen by the naked eye in the final photo. This is called "white balance". Most cameras provide the function of "automatic white balance", but under different light sources, this system still can't fully meet people's visual requirements. Therefore, more accurate cameras provide users with a series of light source choices, such as: sunlight (color temperature 6000K), cloudy days-(color temperature 3500-3000K), fluorescence-generally used in indoor sunlight environment (fluorescence-color temperature 5500K-4000K), burning light-indoor strong light (incandescence -3500 K). Generally, manual and automatic white balance adjustment methods are provided on the display stand. There is a video amplifier in the camera, which amplifies the signal from CCD to a usable level. Its magnification is gain, which is equivalent to high sensitivity. However, in bright lighting environment, the amplifier will be overloaded, which will distort the video signal. When the switch is turned on, the lens aperture is completely opened in the case of low brightness, which automatically increases the gain and obtains a clear image. When the switch is closed, natural and low-noise images can be obtained at low brightness.