The focus of photography

The lens of the camera is equivalent to the convex lens in the convex lens experiment, and the negative film is equivalent to the light screen. Camera focusing means that when the distance between the object and the lens changes, the image distance should be adjusted according to the object distance. In order to control the exposure properly, the aperture should be adjusted and the exposure time can also be controlled by the shutter.

So the answer is: adjust the image distance according to the object distance; Aperture; shutter