Nikon AF-S NIKKOR 400mm f/2.8G ED VR Manuel D'utilisation page 24

4. Focusing
Set your camera's focus mode selector according to this chart:
En
Autofocus with manual override (p. 21)
A/M mode: Autofocus with manual override. AF priority
M/A mode: Autofocus with manual override. MF priority
1 Set the focus mode switch to "A/M" or "M/A". (Fig. 1)
2 You can manually override autofocus by operating the
focus ring while lightly depressing the shutter release
button or the AF start button on the camera or the
Focus operation button on the lens.
• To cancel manual override, remove your finger from the shutter
release button or the AF start button on the camera or the Focus
operation button on the lens, and lightly depress the shutter release
button to return to the autofocus mode.
5. To limit the range of autofocus
(See page 20 for usable cameras.)
• With AF operation, if the subject is always more than
6m (19.7 ft) away, set the focusing limit switch (Fig. 2)
to "∞–6m" to reduce focusing time.
24
Fig. 1
Fig. 2