Sharpness at 300mm

For this test, the Canon RF 100-300mm F2.8L IS USM lens was attached to a Canon EOS R5 body, which was in turn mounted to a sturdy tripod. Exposure delay mode was actVated. Tonal and colour variance across the crops are due to change in natural light during the session.

The full frame at 300mm

Centre sharpness remains high through from f/2.8 to f/16, with f/22 being adversely affected by diffraction.

The edges aren't quite as sharp as the centre, with f/4-f/11 producing the sharpest results.

Aperture	Centre Crop	Edge Crop
f/2.8
f/4
f/5.6
f/8
f/11
f/16
f/22