A camera is a machine that converts optical image signals into electrical signals for storage or transmission. When we shoot an object, the light reflected by the object is collected by the camera lens and focused on the light receiving surface of the camera device (such as the target surface of the camera tube), and then the light is converted into electric energy by the camera device, and a "video signal" is obtained. The photoelectric signal is very weak, so it needs to be amplified by pre-amplifier circuit and then processed and adjusted by various circuits. The final standard signal can be sent to video recorders and other recording media for recording, or spread through a propagation system, or sent to a monitor for display.