Sharpness at 300mm

The sharpness tests for this review were carried out using a real-world subject rather than a test chart. The Tamron 28-300mm f/3.5-6.3 Di VC PZD lens was attached to a Canon EOS 5D Mark III 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

Center sharpness is not very good, only really being just about acceptable between f/8 and f/11, with some softness evident wide open at f/6.3. At f/16 sharpness is beginning to drop off a little due to diffraction. You need to stop down to f/16 to obtain any level of edge sharpness.

Aperture	Centre Crop	Edge Crop
f/6.3
f/8
f/11
f/16
f/22
f/32
f/40