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My R lenses don't have focus shift issues, and the R matte viewscreens are responsive enough and accurate enough for active birds.
or a weasel running toward the camera
Can focus peaking in an EVF keep up with these subjects?
yes, unless that falcon was in a stoop straight at you in which case i doubt even you would be able to see the difference between almost accurate focus and dead on focus no matter what the viewfinder was. obviously not all focus peaking/evfs are created equal. i've not heard much about how this one will compare to the sony ones i've used.
the problems with accuracy of peaking come primarily from super speed lenses wide open where spherical aberration confuses the focus plane and from stopped down wide angles where nearly everything is close to in focus (thus causing everything to peak). i don't think either of these issues would be much of a problem for you in most of your shooting. i find peaking to be quite accurate using telephoto lenses. it is not as enjoyable a feeling though as looking through a nice ground glass screen and you have to train your eyes to look for different focus cues.