Cameras

Ideal pinhole camera	Real pinhole camera
Aperture with a lens system	Why is depth-of-field limited?

Camera Elements

The aperture is the diameter of the lens opening, most often specified as a fraction of the lens focal length. For a typical 50mm lens, the aperture may range from f/2 (large aperture) to f/22 (small aperture). The aperture will determine the depth of field of the resulting image.