Being both prone to idle curiosity and by nature inclined to pixel peeping, I decided to test my hypothesis (instrumental in my purchase of a D810) that the D810 with 70-200 F4 was superior at suppressing shutter slap issues when judged against the Sony A7R with FE 70-200 F4.
I shot a series of handheld shots on both cameras, alternating, at 200mm and at two different combinations of shutter speed, ISO and aperture.
The second series was shot at a shutter of 100th of a second and, as I suspected, showed a very clearly superior performance from the Nikon. Here is a totally representative pair of frames, one from each camera. Guess which is which:
So far, so good and very much as I expected: the inability of the A7R to work for shots of this sort has really been cramping my style. Sorted.
But the next series were shot at F5.6 and 1/320th. This is usually not quite into the safe zone for the Sony, which seems to generally need shutter speeds of 2x focal length even with stabilisation on. However, I was feeling lucky and was able to partially brace against a door frame and in the event the Sony shot worked out to be approximately as free of camera shake as the Nikon. But a very curious thing became apparent as I looked at the files: Both cameras are roughly equally sharp on the central part (the middle 'twin set' of windows, which was also the point of AF) BUT the Nikon frame is softer at the bottom (see the red door and surround) and the Sony is sharper at the top (see the crenellations).
I have my theories, but would be curious to hear what others think? This effect was replicated across a series of frames,
BTW one nice thing about the partial return to Nikon is, no more jaggies: take a look at the crenellations and the diamond-shaped ventilation panes in the upper windows in both images.
Click on each image to load a full sized version: