Nikon D750 DSLR Camera (Body Only) - Manual (Page 370)

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If Off is selected, the control panel backlight (LCD illuminator)
will only light while the power switch is rotated toward D . If On
is selected, the control panel will be illuminated whenever the
standby timer is active (
0 39). Select Off for increased battery
life.
d10: LCD Illumination
G button
➜
A Custom Settings menu