Sharpness at 18mm

For this test, the Sigma 12-24mm F4 DG HSM Art lens was attached to a Canon EOS 5DS R body, which in turn was mounted on a sturdy tripod. Exposure delay mode was activated. Tonal and colour variances across the crops are due to changes in natural light during the session.

The full frame at 18mm

Centre sharpness remains high through from f/4 to f/11, with f/16 and f/22 being adversely affected by diffraction. The edges aren't quite as sharp as the centre, with f/5.6-f/11 producing the sharpest results.

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