Light reflects from the scene being photographed and strikes the lens of the camera. The light passes through the lens and forms an upside down image on the film at the back of the camera. The image can be sharpened by adjusting the distance between the lens and the film. Many cameras have a focusing mechanism by which the photographer moves the lens a short distance to sharpen the image. In addition, most cameras have a viewfinder, a sighting instrument that the photographer looks through to frame the subject.
Most cameras also have a film advance.
With this device, the photographer winds the film through the camera to put unexposed film in position to take a picture. After each picture has been taken, the film advance moves the exposed film out of the way. The film advances automatically in many cameras. Controlling the light. To take good pictures, a camera must let the proper amount of light reach the film.