AGeoJO wrote:
For lenses which are focused wide open in AF-S mode, Sony does not correct for focus shift. The PDAF cycle which acquires the fast initial focus is followed by a CDAF confirmation cycle, both of which occur with the lens wide open. For the camera to correct for the shift in AF-S it would need to change the CDAF cycle to occur with the lens stopped to its shooting aperture...or always focus the lens stopped down like it does other lenses like the 24-70GM. If I'm understanding your question correctly
Sony could correct focus-shift using a software offset table that compensates per fl and aperture. So the focus would be slightly moved whenever the aperture is changed and any focus shift in the lens design effectively compensated. If such a calibration table would somehow be out of whack, the result would rather precisely match what is reported. As in the focus is lost simply by changing the aperture.
I'm just guessing here as my own copy seems flawless (A7R2, FW4.0, lens version 01).
Feb 03, 2018 at 11:25 AM
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