You could, Jack, with the R5 in burst mode - one shot is bound to be shake-free! All of mine were pretty good. I prefer to be at 1/320s or faster at this focal length and upped the iso 3x for another set of shots but it wasn't necessary. The take home message for me, personally, is that as I have a good 100-400mm II and TCs, there is no point in my considering an 800mm f/11 as I don't think it will be sufficiently sharper to warrant a second lens.
So, now what are your thoughts regarding the R5 and zoom lens vs the D500 and 500 PF? I'm really curious, since I will get the R5 (my funds are building nicely) whether I'll be satisfied with the 400 DO X2 (I'm confident there won't be an issue with X1.4).
From my comparisons at 20m, the Nikon D850 + 500mm PF + 1.4xTC at 700mm resolves more and has more contrast than the 100-400mm II + 2xTC on the R5. At close distances, the Nikon outresolves and has better contrast still with the various combinations of TCs at similar magnifications. Whether that makes enough difference in practice, is another matter. It's not enough for me to use one or the other exclusively. When looking at really fine details, like insects or small fish in birds beaks, then you will see a difference.
I took out the D850 + 500PF, after weeks of not using them, for a brief walk around a local field, where I usually see nothing other than crows or pigeons. Suddenly, a pair of Green Woodpeckers started flying. There was no time to carefully track as they were flying low and very fast against a background but the DSLR locked on immediately. Here they are, upresolved by a factor of two because the images were only about 300-400 pixels long. I am not sure the R5 would have been able to capture these as they were so small, and the sharpness of the prime was needed to get a reasonable image at this size. But, maybe the R5 could.
That is impressive. So the question then is, why do you now have the R5? Is there a significant weight difference?
The R5 is up there with the best of the mirrorless and its eyeAF make it better than a DSLR in quite a few situations, and Canon has great lightweight zooms. The D850 and D500 are the best DSLRs in their class and have the 500mm PF, which make for a great DSLR viewing experience for looking at wildlife. For reliable locking on to a small bird in foliage, a DSLR with point focus is difficult to beat whereas mirrorless can get distracted. On the other hand, once the R5 locks on, it sticks like glue when the bird hops around or takes off.
- OK, I will use the opportunity, Bert63 is to blame, not me - never!) but just compare it with the opportunity to see and take even crap shots of bird #7 counted from 1907!!!!).!!!! On other hand (OK here I'm going wildly optimistic) it could be just temporary "absentee" (ha, ha even I don't believe myself)!
