Nikon D780 DSLR Camera (Body Only) - Manual (Page 177)

131 Shooting Settings
D DX Lenses
DX lenses are designed for use with DX format cameras and have a
smaller angle of view than lenses for 35 mm format cameras. If [
Auto DX
crop ] is off and an option other than [ DX (24 × 16) ] (DX format) is
selected for [ Choose image area ] when a DX lens is attached, the edges
of the image may be eclipsed. This may not be apparent in the viewfinder,
but when the images are played back you may notice a drop in resolution
or that the edges of the picture are blacked out.