It definitely does make comparisons harder, that’s for sure. I think that I’ve accounted for that in my judgements, but I do intend to test with a flatter subject as well, to see how that looks and if it changes the conclusions (the problem with a flat subject is that it’s hard to be certain you nailed focus – at least with this ‘deep’ subject you can tell where the focal plane actually is, when it gets narrow enough that it matters).

There’s also a meta-observation worth noting, about AF accuracy. e.g. the 80-400 seemed prone to back-focusing (see the follow-up post), whereas the 100-400 has been much more consistently accurate (in these “studio” tests as well as initial real-world use).