Nikon 13187 User Guide (en)

Calculating Angle of View
The D600 can be used with Nikon lenses for 35mm (135) format cameras. If Auto DX crop is 
on (
0 90) and a 35mm format lens is attached, the angle of view will be the same as a frame 
of 35mm film (35.9 × 24.0 mm); if a DX lens is attached, the angle of view will automatically 
be adjusted to 23.5 × 15.7 mm (DX format).
If a 35 mm format lens is attached, the angle of view can be reduced by 1.5 × by turning Auto 
DX crop
 off and selecting DX (24×16).
The DX (24×16) angle of view is about 1.5 times smaller than the 35mm format angle of 
view. To calculate the focal length of lenses in 35mm format when DX (24×16) is selected, 
multiply the focal length of the lens by about 1.5 (for example, the effective focal length of a 
50mm lens in 35mm format would be 75 mm when DX (24×16) is selected).
FX (36×24) picture size (35.9 × 24.0 mm,
equivalent to 35mm format camera)
Picture diagonal
DX (24×16) picture size (23.5 × 15.7 mm,
equivalent to DX format camera)
Angle of view (FX (36×24); 35mm format)
Angle of view (DX (24×16); DX format)