Sharpness at 300mm

The sharpness tests for this review were carried out using a real-world subject rather than a test chart. The Sigma 100-400mm F5-6.3 DG DN OS 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 300mm

Centre sharpness is a little soft wide-open at f/6.3. Both the centre and the edge remain high through from f/8 to f/16, with f/22 to f/29 being adversely affected by diffraction.

Aperture	Centre Crop	Edge Crop
f/6.3
f/8
f/11
f/16
f/22
f/29