Depth of field refers to the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image. Small or shallow depth of field emphasizes the subject by making the rest of the photograph appear unfocused, while large depth of field means practically the entire image has sharp definition.

1. Depth of field (DOF) in a photograph
• DOF: “distance between the nearest and farthest
objects in a scene that appear acceptably sharp in
an image” (http://en.wikipedia.org/wiki/Depth_of_field)
Photo published on Flickr by Fogview under a CC
BY-NC-SA 2.0 license
Small or shallow DOF: the subject is
Photo published on Flickr by emphasized at the expense of the rest
Jennifrog under a CC BY 2.0 license of the photograph, which appears
Large DOF: practically unfocused. A typical example is a
the entire image has a macro shot, i.e. a close-up of a subject
sharp definition. at greater than life size.