Nikon D7500 User Manual page 310

A
Calculating Angle of View
The size of the area exposed by a 35mm camera is 36 × 24 mm. The size
of the area exposed by the D7500 when DX (24×16) is selected for
Choose image area in the photo shooting menu, in contrast, is 23.5 ×
15.7 mm, meaning that the angle of view of a 35mm camera is
approximately 1.5 times that of the D7500 (when 1.3× (18×12) is
selected, the size of the area exposed decreases, further reducing the
angle of view by about 1.3×).
1 Lens
2 35 mm format picture size (36 × 24 mm)
3 Picture size when DX (24×16) is selected for Choose image area
(23.5 × 15.7 mm)
Picture size when 1.3× (18×12) is selected for Choose image area
4
(18.0 × 12.0 mm)
Picture diagonal
5
6 35 mm format angle of view
Angle of view when DX (24×16) is selected for Choose image area
7
Angle of view when 1.3× (18×12) is selected for Choose image area
8
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