Sharpness at 100mm

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 100mm

At 100mm, centre sharpness is very good at the widest aperture of f/4.5. It is ever so slightly sharper at f/5.6, and remains extremely sharp up until f/16. By f/22, softness is noticeable, while f/32 and f/36 (the narrowest aperture at this focal length) are very soft. You may not notice the softness when viewing the image at normal printing or web size, but it’s still best to keep to the optimum apertures for ultimate sharpness. At the edges, the sharpest images at taken between f/11 and f/16.

Aperture	Centre Crop	Edge Crop
f/4.5
f/5.6
f/8
f/11
f/16
f/22
f/32
f/36