In every photo there'll be a range around the chosen focus
distance that appears to be sharp. This range is called the
"Depth-of-Field". The following slide show demonstrates the
effect of different aperture settings regarding the depth-of-
field within a scene. The lamp is the point of focus here.
Select one of the shown aperture settings and observe the effect
on the background (the castle) - requires The depth-of-field is
dependent on the OBJECT MAGNIFICATION ON THE FILM and the chosen
aperture at a specific focal length. At theoretical f/1.0 the
DOF is the same for all focal length and the same object
magnification. However, stopping down changes the DOF
differently depending on the focal length. The increase of DOF
is bigger towards shorter focus distances. Whatever aperture you
choose - the sharpest point is located at the chosen focus
distance. The sharpness around it will deterioate more or less
rapidly dependent on the distance from the focus plane and the
chosen aperture. The larger area of the Depth