inksandpaper wrote:
That's strange. Shimming tilt at the mount does not cause FC to increase significantly. I wonder what's going on. What do you mean by the focus distance reported was less accurate? How much less accurate was it? Is it commensurate with the focus shift you would expect on-axis for a 10-micron correction induced at the screw, which is ~5 microns only on-axis?
Yes, I was susprised to see the induced FC given how thin the shim was. Past about 1m, the in-camera distance readout was increased significantly. E.g. objects at ~2m were sharpest for a readout of about 4m, whereas unshimmed it was actually surprisingly accurate. I rely on such distance readouts to do my focus stacking, so this strange readout remapping might make that quite challenging. I'm not sure how to calculate how much focus shift I should expect.
But the whole affair has remined me why I was so glad to see more high IQ native lenses released for the Sony E system after messing around with shimmed adapters in the early days.
Sep 16, 2020 at 05:07 PM
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