Sharpness- and aberrations-wise, how does it compare with primes at similar apertures, as well as with the Canon 24-70L II (which has a well-deserved reputation for being prime-sharp)?
I have never used the Canon, so I cannot compare. I have heard excellent things about it obviously.
Relative to the 2 Otii that I have been using predominantly these past months, I haven't done a 1:1 comparison in controlled conditions and also only used the lens at f2.8 when I thought it was required, but my overall feeling is that it is plenty sharp at the apertures I used most this time (anywhere between f4 and f11). Does it have the same level of magic when things are done perfectly right? Probably not, but nothing does really.
There is just no way a zoom costing not much more than half of an Otus, equipped with AF, stabilization and fully weatherproofed could be at the same level of optical quality as the best prime ever designed without any of those major design constraints.
What is pretty clear is that I would probably not have gotten at least the 2 last images in the series here because those moments lasted less than 0.5 sec (the old lady started to smile and the cute girl stopped smiling
), and I would not have been able to reliably manually focus the Otus in such a time frame. For the first 3, tripods were not authorized and stabilization helped a lot keep the ISO reasonably low.
In terms of CA, I have only checked casually the C1 conversions, knowing that C1 does correct some stuff automatically, and have not noticed any obvious issues. Overall I feel that aberations are pretty well controlled.
I know this isn't very accurate, sorry, but I am not a lens tester.
Cheers,
Bernard