On a digital SLR camera, an AF (
auto-focus) Servo refers to the capability of the
camera to continuously focus on a moving subject. When using the camera, you would normally press the shutter button to a halfway point, allow the camera’s auto-focus to engage, then press the shutter button all the way down to capture the subject.
See also auto-focus.
Also see The Digital Camera Picture” in Webopedia’s Quick Reference section.