Depth-of-Field (DOF) is “the portion of a scene that appears acceptably sharp in the image.”. wikipedia.com
The DOF is controlled by the lens Aperture diameter within the lens. An aperture of F2.8 or less will create a very shallow DOF and is often used for Portrait Photography. Opening Up (increasing your aperture) to F11 or greater will create a deep DOF and this effect is often used for Landscape Photography. By understanding the Apertures on your lens, you will be able to Pre-visualize your Depth-of-Field and begin to control the effects within your photographs.
The photograph above is an example of a Shallow Depth-of-Field where the subject is in focus but the foreground and background are out-of-focus. The exposure was set at F2.8, 1/125 at 400ISO.
Above is an example of a Deep Depth-of-Field where the landscape photograph is completely in focus. The exposure was set at F16, 1/60, 800ISO.
“Depth of Field.” wikipedia.org 2010. Wikimedia Foundation Inc. 9 February 2010.

