Less expensive cameras have a fixed lens position and aperture, with diameter D f. In the limit, D 0, you don’t even need a lens: the camera is a pin-hole camera: only “one ray” from each point on the object reaches the CCD/film. Cameras in cell phones typically replace the mechanical shutter with an “electronic shutter” which turns the pixels in the CCD detector on/off. Also, better cell phone cameras have an autofocus, that moves the lens slightly to get better focus.
