Nikon D750 DSLR Camera (Body Only) - Manual (Page 403)

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Memory cards must be formatted before first use or after being
used or formatted in other devices.
Note that formatting
permanently deletes all pictures and other data on the card . Before
formatting, be sure to make backup copies as required ( 0 266).
Selecting Format memory card in the
setup menu displays the options shown
at right; choose a memory card slot and
select
Yes to format the selected card.
Memory cards can also be formatted by
holding the
O ( Q ) and Z ( Q ) buttons
down simultaneously until a flashing C appears in the
shutter-speed displays in the control panel and viewfinder.
Format Memory Card
G button
➜
B setup menu
D
During Formatting
Do not turn the camera off or remove memory cards during formatting.
O ( Q ) button Z ( Q ) button