Nikon Z 50 Reference Manual page 316

The following options are available:
Option
K
Select center
focus point
A
AF-ON
F
AF lock only
E
AE lock (Hold)
D
AE lock (Reset
on release)
C
AE lock only
B
AE/AF lock
r
FV lock
h
Flash off
q
Preview
1
Bracketing
burst
288 Menu Guide > A Custom Settings
Pressing the control selects the center focus point.
Pressing the control initiates autofocus.
Focus locks while the control is pressed.
Exposure locks when the control is pressed, and
remains locked until the control is pressed a
second time or the standby timer expires.
Exposure locks when the control is pressed, and
remains locked until the control is pressed a
second time, the shutter is released, or the
standby timer expires.
Exposure locks while the control is pressed.
Focus and exposure lock while the control is
pressed.
Press the control to lock flash value for the built-in
flash or optional flash units. Press again to cancel
FV lock.
If the flash is currently enabled, it will be disabled
while the control is pressed.
Keep the control pressed to preview color,
exposure, and depth of field.
If the control is pressed while exposure or ADL
bracketing is active in single frame release mode,
all shots in the current bracketing program will be
taken each time the shutter-release button is
pressed. If white balance bracketing is active or a
continuous release mode is selected, the camera
will repeat the bracketing burst while the shutter-
release button is held down.
Description