- Sep 26, 2021
Thanks, that's quite helpful. I've been getting more interested in trying out bird photography, and I've put my EF 70-200 f/2.8 III or 55-250 STM on my 80D for more reach, but it's not really long enough.There aren't much data out there, and I have never handled an RF 600mm f/11. So, here is my indirect opinion. Canon's own MTF values and the-digital-picture show clearly that the RF 100-500mm is significantly sharper and with better contrast at 500mm than the RF 600mm. My 100-400mm II + 1.4x TC at 560mm is pretty close to the Rf 100-500mm in sharpness and contrast. My very good copy of the Sigma 150-600mm C at 600mm had similar resolution but poorer contrast than my 100-400mm II at 560mm, and was definitely inferior to my RF 100-500mm - the RF cropped from 500 was better than the 150-600mm C at 600mm. I would guess that the weaker performance due to diffraction at f/11 of the RF 600mm is not far from the performance of the 150-600mm at f/6.3, which is n ot optimised for optical quality at the longest end. I found the AF and the IS of the Sigma much below those of the Canon lenses on the R5.
I've been considering purchasing a longer telephoto but I can't decide whether to go with the RF 600 f/11, Rf 800 f/11 or wait for the RF 100-400 f/8 when that comes out, to use on my RF mount camera, or to go with something like the Sigma 100-400 or 150-600 on the crop body. The images I've seen from the RF f/11 lenses always look dark to me, like they're shot through a ND filter, guessing that's due to the narrow aperture. I've only ever shot that aperture for macro from an inch or two away!
The prices of the Canon EF 100-400 ($3500) or RF 100-500 ($5000) in my part of the world are hard to justify, even though the exchange rate isn't double, Canon likes doubling the prices here, an R5 with an RF 100-500 is a $10,500 setup!