Nikon F4 Instruction Manual page 38

3.
Lightly press shutter release button to start Focus Tracking.
38
4.
Confirm both arrows
( ~
.... ) appear in the viewfinder, then
fully depress shutter release button to take an in-focus
picture.
- With Focus Tracking, even if the subject is in focus, the in-
focus indicator (e ) does not appear.
- If the
subject speed becomes erratic, Focus Tracking will
be automatically deactivated and standard continuous
focusing will operate.
- Focus Tracking ability will vary according to subject's
brightness and movement, lens in use and shooting
distance.
- During Focus Tracking, the subject must remain within the
focus brackets.