Справочник Пользователя для Nikon D2HS

If the camera autofocus system detects that the subject is moving when the shutter-
release button is pressed halfway, it will au to mat i cal ly ini tiate pre dic tive focus track ing.  
If the sub ject is mov ing toward or away from the cam era, the camera will track focus 
while at tempt ing to predict where the subject will be when the shutter is re leased.  In 
single-servo autofocus, the camera will initiate pre dic tive focus tracking if the sub ject 
was moving when the shut ter-release button was pressed halfway.  Fo cus will lock 
when the subject stops moving.  In con tin u ous-servo AF, the camera will also initiate 
predictive focus tracking if the subject starts mov ing after the shutter-re lease button is 
pressed halfway.  Focus will not lock when the sub ject stops moving.

Predictive focus tracking is not available in manual focus mode.

If Focus is selected for Custom Setting a1 (AF-C mode priority), photographs can be 
taken in continuous servo-AF only when the camera is in focus.  Select FPS rate + AF 
for improved focus during continuous shooting.

If Release is selected for Custom Setting a2 (AF-S mode priority), photographs can 
be taken in single servo-AF even when the camera is not in focus.

If AF-ON only is selected for Custom Setting a5 (AF activation), the camera will only 
focus when one of the AF-ON buttons is pressed, not when the shutter-release button 
is pressed halfway.

Custom Setting a8 (Vertical AF-ON) controls whether the AF-ON button for vertical 
shooting is used to initiate autofocus, select the focus area, or both.

If desired, the AE-L / AF-L button can perform the same function as the AF-ON button.

For the purpose of focusing the camera, pressing either of the AF-ON buttons has the 
same effect as pressing the shutter-release button halfway (the AF-ON button for verti-
cal shooting can only be used when the shutter-release button for vertical shooting is 
unlocked).