Nikon D750 DSLR Camera (Body Only) - Manual (Page 359)

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Choose whether separate focus points can be selected for
“wide” (landscape) orientation, for “tall” (portrait) orientation
with the camera rotated 90 ° clockwise, and for “tall” orientation
with the camera rotated 90 ° counterclockwise.
Select No to use the same focus point regardless of camera
orientation.
Choose Yes to enable separate focus-point selection.
a8: Store Points by Orientation
G button
➜
A Custom Settings menu
Camera rotated 90 °
counter-clockwise
Landscape (wide)
orientation
Camera rotated 90 °
clockwise
Camera rotated 90 °
counter-clockwise
Landscape (wide)
orientation
Camera rotated 90 °
clockwise