Sharpness at 70mm

For this review, the sharpness test is carried out by photographing a real-world sample, rather than a test chart. The Canon EF 70-300mm f/4-5.6 IS II USM Lens was mounted on a Canon EOS 5D Mark IV, which was in-turn mounted to a sturdy tripod. Exposure delay mode was activated to prevent camera-shake. Any changes in tone you might see across the crops are due to natural light changes during the shooting session.

The full frame at 70mm

At the centre, sharpness is very good wide open (f/4), but is sharpest between f/5.6 and f/11. At f/16, sharpness is a little softer, but still very good. At f/22 it's softer again, and very soft at the narrowest aperture for this focal length (f/32). If you’re viewing the image at normal printing sizes, it's not quite so obvious though. At the edge of the image, sharpness is best between f/8 and f/22, before dropping off again at f/32.

Aperture	Centre Crop	Edge Crop
f/4
f/5.6
f/8
f/11
f/16
f/22
f/32