Depth of field (DOF) refers to the amount of a scene in the “sharp” range. Shallow DOF is typically characterized by heavily blurred backgrounds that you might see in outdoor portraits. Deep focus (opposite of shallow DOF) is typically characterized by tack sharp landscapes with no visible blur.
The most widely accepted method for controlling DOF is aperture, or f-number. This is certainly a feasible and convenient way to control DOF, but there are other factors at play. Just like exposure is controlled by three factors (ISO, shutter speed, and aperture), DOF is controlled by three main factors. Let’s take a look at these three factors and how you can use them to your advantage.
Helderberg Photographic Society 