Sharpness at 300mm

The sharpness tests for this review were carried out using a real-world subject rather than a test chart. The Tamron 100-400mm F/4.5-6.3 Di VC USD lens was attached to a Canon 5DS R 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

Both center and edge sharpness are good wide-open at f/6.3 and excellent from f/8 through to f/16. At f/22 sharpness is beginning to drop off due to diffraction.

Aperture	Centre Crop	Edge Crop
f/6.3
f/8
f/11
f/16
f/22
f/32
f/45