Nikon D3S - A4: Focus Tracking with Lock-On; A5: AF Activation

298
U
This option controls how autofocus adjusts to sudden large
changes in the distance to the subject during continuous-servo AF.
If Shutter/AF-ON is selected, both the
shutter-release button and the B button
can be used to initiate autofocus.
If AF-ON
only is selected, autofocus is only initiated
when the B button is pressed.
a4: Focus Tracking with Lock-On
G button ➜ A Custom Settings menu
Option Description
C 5 (Long)
When the distance to the subject changes abruptly, the
camera waits for the specified period before adjusting
the distance to the subject.
This prevents the camera
from refocusing when the subject is briefly obscured by
objects passing through the frame.
( 4
D 3 (Normal)
) 2
E 1 (Short)
Off
The camera immediately adjusts focus when the
distance to the subject changes.
Use when
photographing a series of subjects at varying distances
in quick succession.
a5: AF Activation
G button ➜ A Custom Settings menu