a3 Focus Tracking with Lock-On
Explanation: „Lock-On“ means that the continuous autofocus reacts with a delay if the distance to the subject changes suddenly. This prevents wrong reactions of the autofocus e.g. if someone walks through your viewfinder image. On the other hand it can make autofocus reactions slower.
The period for „lock-on“, i.e. for how long a sudden change in distance is tolerated can be chosen in five levels from short to long or set to zero (off).
Tips: I leave the standard setting „nomal“ and am happy with the continuous autofocus.
Depending on your shooting situation another setting may be better – try a longer setting if you get unwanted focus movements back and forth and a shorter setting if you want to get it to react quicker.