Nikon received reports that when photographing scenes in which a bright light source, such as the sun or high-intensity lighting, sits at a certain position along the top border of the frame, flare with an unnatural shape may occur.
Affected cameras are identified by serial number using the checker on Nikon's advisory page. Nikon service centres inspect and service the light-shielding components and adjust the autofocus sensor position free of charge. Nikon states the work does not affect autofocus precision or any other camera function.
A black dot inside the tripod socket indicates that the flare measures have already been applied to that body — a useful check when buying used.
Nikon notes that even after this service, all digital SLR cameras may still exhibit flare in backlit scenes.