I'm interested in this issue, too.
I just started this thread on focus shift at DPReview:
http://www.dpreview.com/forums/post/56363973
One of the things I like about my A7II is that it can easily focus with the lens stopped down to taking aperture. This avoids issues with focus shift that are somewhat common with SLRs. In fact, this is one of the reasons I transitioned to mirrorless cameras.
I am hearing from owners of A7RII cameras that the new camera's aperture opens up to focus, then stops back down to taking aperture, just like an SLR. This is a change from what the other A7 cameras do, AFAIK. I am wondering if this is causing any issues with focus shift.
Two things piqued my interest in this question recently. One is a review of the Batis 85mm lens on Luminous Landscape. In a series of photos of a truck, carefully focussed by Michael Reichmann using an A7RII on a tripod, there is clear evidence of front focus when the Batis is stopped down. Also, there have been at least four reports of zoom lenses front-focussing with the new camera. (example: http://www.dpreview.com/forums/post/56362175).
I wonder if others have experienced focus shift with any lenses on the A7RII, or are these reports just statistical outliers? Maybe just bad lenses?
I would be very curious to know if the A7RII opens the lens aperture part way or all the way in order to focus?
If it just opens up to f3.5 or so, this would probably eliminate most of the potential problems with focus shift. If it opens to f1.8 or f1.4 to focus, that seems to be inviting focus shift with lenses that are prone to it.
In that case, we would be back to where we were with SLRs--making sure our lenses have no focus shift, or else managing the shift as best we can.
Finally, I wonder what the A7RII's behavior is when back-button focus is used. Does the aperture still open up to focus when the camera is in this configuration?
Thanks for any information or insights.
-- hide signature --
d
In thinking this over, I'm realizing that most focus shift is to the back, not the front. So maybe these reports are unrelated to aperture behavior.
Still, I'd love to know from A7RII users here if the aperture actually opens up all the way to focus, or just part way. And what happens when you use back button focus?
--d