Sharpness at 105mm

For this test, the Sigma 24-105mm F4 DG OS HSM lens was attached to a Canon EOS 5D Mark III 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 105mm

Centre sharpness remains high through from f/5.6 to f/16, with f/22 being adversely affected by diffraction. The edges aren't nearly as sharp as the centre, with f/8-16 producing the sharpest results.

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