What is the relationship between the focal length of the camera lens and the viewing angle and the size of the image?

The relationship between focal length and viewing angle The focal length of a lens determines the viewing angle of the lens. Usually, when the distance between the shooting position and the object is constant, the shorter the focal length of the lens, the wider the viewing angle and the larger the shooting range, and the smaller the image formed by the object; Conversely, the longer the focal length of the lens, the narrower the viewing angle, the smaller the shooting range and the larger the image formed by the lens.

The viewing angle of the lens is also related to the border size of the formed image. The shorter the focal length, the larger the image size; The longer the focal length, the smaller the image size.