Sharpness at 20mm

For this test, the Sony FE 20-70mm F4 G lens was attached to a Sony Alpha A7R IV 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 20mm

The centre is pleasingly sharp even wide open at f/4, with peak performance achieved in the f/5.6-f/11 range. Diffraction starts to set in at f/16.

The edges are almost as sharp as the centre, with f/5.6 to f/11 again being the optimum settings.

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