The Sub-Selector; Focus-Point Selection; Autoexposure (Ae) Lock; Focus Lock - Nikon Z 7 Reference Manual

The Sub-Selector

Use the sub-selector as a joystick to
select the focus point, or press the center
to lock focus and/or exposure.

Focus-Point Selection

Use the sub-selector to select the focus
point in the shooting display. Focus-
point selection is not available when
auto-area AF is selected for AF-area
mode (0 54).
Focus point

Autoexposure (AE) Lock

Pressing the center of the sub-selector locks exposure at the
current setting. AE lock can be used to recompose shots after
metering a subject that will not be in the selected focus area in
the final composition, and is particularly effective with spot or
center-weighted metering.

Focus Lock

The center of the sub-selector can be used to lock focus on the
current subject when AF-C is selected for focus mode. When
using focus lock, choose an AF-area mode other than auto-area
AF.
86 Shooting Controls