Full-time-servo AF or AF-F is used for moving subjects. When set to AF-F, the camera will focus continuously as long as the shutter release button is pressed. The focus locks when the shutter button is pressed halfway. AF-F is one of the focus modes that are availalble on select cameras when in Live View.nikongrossary
A system that allows the photographer to turn the lens manual focusing ring and instantly override autofocus while the lens AF/MF switch is still in the autofocus mode. More than half of Canon s EF lenses with Ultrasonic Motors have this feature.