Nikon D6 Reference Manual page 137

D
The J Button
While pressing 2 or the center of the multi selector generally has the
same effect as pressing J , there are some items for which selection can
only be made by pressing J .
D
Grayed-Out Items
•
Some items and menu options may be
unavailable depending on camera status.
Unavailable items are displayed in gray.
• In some cases, pressing J when a grayed-out
item is highlighted will display a message
explaining why the item is unavailable.
The G Button 85