Sharpness at 135mm

Our sharpness tests are carried out by photographing a real-world subject rather than a test chart. The Tamron 70-300mm F4.5-6.3 Di III RXD was attached to a Sony A7 III, which in turn was mounted on a sturdy tripod. Self-timer mode was activated to steady the camera completely. Any slight tonal changes you may see across the crops are a result of slight changes in natural light during the shooting session.

The full frame at 135mm

Center sharpness is very good wide open at f/5 and excellent between f/5.6 and f/11. At f/16 to f/22 sharpness across the frame is beginning to drop-off due to diffraction.

Edge sharpness isn't quite as good, with f/5.6 to f/11 producing the best results.

Aperture	Centre Crop	Edge Crop
f/5
f/5.6
f/8
f/11
f/16
f/22
f/25