Field of view
Slide from 10 to 70mm and watch the frame tighten. The nested rectangles show how much less of the same scene each longer focal length captures.
Same scene; each frame is what that focal length sees.
Angle of view36.8°
Full-frame eq.53 mm
10-20 G10–20 mm
17-70 VC17–70 mm ✓
Horizontal angle of view is 2·atan(23.3 / 2f) degrees, using
the sensor's 23.3 mm width. Multiply the focal length by the
1.5× crop factor for the full-frame equivalent — so your 10mm sees
like a 15mm, and your 70mm like a 105mm.