Cameras 101: What is Depth of Field?
Depth of field, or DOF, indicates how much of the image you choose to put in focus. When you choose a subject to focus on in the foreground but leave the background blurry, that's shallow DOF. Deep DOF leaves you with a sharp photograph in both the foreground and background. To change your DOF, change the aperture or f-stop number when you set up a shot on your digital camera. A small number for an aperture will give you a shallow depth of field shot, whereas large numbers are better for detailed images.
Uses of Shallow Depth-of-Field
Uses of Deep Depth-of-Field