Nikon D780 DSLR Camera (Body Only) - Manual (Page 725)

679 Menu Guide > B The Setup Menu
Pixel mapping checks and optimizes camera image sensor. If
you notice unexpected bright spots appearing in pictures taken
with the camera, perform pixel mapping as described below.
• Use a fully-charged battery to prevent unexpected loss of
power.
• Pixel mapping is performed with the lens cap (front cap)
attached and the camera viewfinder eyepiece covered by the
supplied eyepiece cap.
Pixel Mapping
G button
U B setup menu