Sharpness at 18mm

For this test, the Nikon Z DX 18-140mm F3.5-6.3 VR lens was attached to a Nikon Z50 body, which was in turn mounted to a sturdy tripod. Exposure delay mode was activated. Tonal and colour variance across the crops are due to change in natural light during the session.

The full frame at 18mm

Centre sharpness is a little soft wide-open at f/3.5, with the optimum sharpness from f/4 through to f/11, and f/16 and f/22 being adversely affected by diffraction.

The edges aren't quite as sharp as the centre, with f/5.6 to f/11 producing the sharpest results.

Aperture	Centre Crop	Edge Crop
f/3.5
f/4
f/5.6
f/8
f/11
f/16
f/22