Nikon D780 Reference Manual page 428

1
Select a picture.
Display a picture in full-frame playback or playback zoom or
select it in the thumbnail list.
2
Choose [Select to send/
deselect].
Press the i button to display the i
menu, then highlight [Select to
send/deselect] and press J . Pictures
selected for upload are indicated by a
W icon; to deselect, repeat Steps 1
and 2.
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