Sharpness at 20mm

The sharpness tests for this review were carried out using a real-world subject rather than a test chart. The Tamron 17-28mm F2.8 Di III RXD lens was attached to a Sony A7 III camera body, which in turn was mounted on a sturdy tripod. Self-timer mode was activated. Slight tonal changes are due to slight changes in natural light during the session.

The full frame at 20mm

Center sharpness is outstanding between f/2.8 and f/16. At f/22 sharpness is beginning to drop off a little due to diffraction. Edge sharpness is best between f/5.6 and f/16.

Aperture	Centre Crop	Edge Crop
f/2.8
f/4
f/5.6
f/8
f/11
f/16
f/22