Nikon D3s Body Only D3S User's Manual - Page 324

a4: Focus Tracking with Lock-On G button ➜ A Custom Settings menu This option controls how autofocus adjusts to sudden large changes in the distance to the subject during continuous-servo AF. Option Description C 5 (Long) (4 When the distance to the subject changes abruptly, the camera waits for the specified period before adjusting D 3 (Normal) the distance to the subject. This prevents the camera )2 from refocusing when the subject is briefly obscured by objects passing through the frame. E 1 (Short) The camera immediately adjusts focus when the Off 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 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. U 298