Nikon D850 Menu Manual page 133

The following options are available:
Option
Preset focus
A
point
K
AF-area mode
AF-area mode
q
+ AF-ON
q
Preview
r
FV lock
Pressing control selects a preset focus point. To
choose the point, select it and press the control
while pressing the AF-mode button until the focus
point flashes. Separate focus points can be
selected for "wide" (landscape) orientation and for
each of the two "tall" (portrait) orientations if
Focus point or Focus point and AF-area mode is
selected for Custom Setting a7 (Store by
orientation, 0 109). If this option is assigned to
the lens focus function buttons, you can select the
preset focus point by pressing and holding a lens
focus function button. Release the button to
restore the original focus point selection.
Highlight this option and press 2 to select an
AF-area mode (3D-tracking excluded). The
selected mode will take effect while the control is
pressed; releasing the control restores the original
AF-area mode.
As for AF-area mode, above, except that pressing
the control also initiates autofocus.
During viewfinder photography, you can preview
depth of field while the control is pressed. During
live view photography, you can press the control
once to open the lens to maximum aperture,
making it easier to check focus; pressing the
control again restores aperture to its original
value.
Press the control to lock flash value for optional
flash units. Press again to cancel FV lock.
Description
133
Menu Guide