An aperture is an adjustable circular opening which allows more light to pass through a camera lens when it is open and less light as it closes. Changing the aperture affects depth of field as well as exposure and is one of the fundamental relationships in photography.
Aperture values (known as an f-stop, or f) on a lens refer the ratio of that lens’ length divided by the diameter of the opening. For example, a 100mm long lens with a 50mm wide aperture opening would have an f-stop value of f/2.0 (100 / 50 = 2), and an f/16 value means that the aperture is 6.25mm in diameter (6.25 x 16 = 100). Wider apertures let more light in and create a shallower depth of field (a small area of focus): smaller apertures let less light in and create a deeper depth of field (a large area of focus). Using Light Field data, Lytro can virtually recreate a full range of aperture diameters from very large to very small, and allows you to control the depth of field in ways that a traditional cameras cannot.