Sharpness at 300mm

For this test, the Canon RF 100-500mm F4.5-7.1L IS USM lens was attached to a Canon EOS R body, which was in turn mounted to a sturdy tripod. Exposure delay mode was activated. Tonal and colour variance across the crops are due to change in natural light during the session.

The full frame at 300mm

Center and edge sharpness are excellent wide open at f/5.6, and outstanding between f/8 and f/16. At f/22 sharpness across the frame is beginning to drop-off a little due to diffraction, but is still commendably high. F/32 and especially f/40 are best avoided altogether.

Aperture	Centre Crop	Edge Crop
f/5.6
f/8
f/11
f/16
f/22
f/32
f/40