Nikon Z9 Mirrorless Camera - Manual (Page 684)

684 A Custom Settings: Fine-Tuning Camera Settings
Choose the focus speed for video mode.
Use [ When to apply ] to choose when the selected option applies.
D Lens Sounds
The sound produced by the lens during focus operations increases with AF
speed. The effect is particularly noticeable at a setting of [
+5 ], so choose
lower values if you find the noise distracting.
g6: AF Speed
G button
U A Custom Settings menu
Option Description
D [ Always ]
The camera focuses at the selected speed at all
times in video mode.
E
[ Only while
recording ]
Focus is adjusted at the selected speed only while
video recording is in progress. At other times, the
camera focuses as quickly as possible.