JimBuchanan
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Fred Miranda wrote:
Focus shift
Below is an example showing focus shift. The image on the LEFT was focused at f/1.2 and captured at f/1.2. The image on the RIGHT was focused at f/4 and captured at f/1.2. Big drop in resolution as you can see.
Good work Fred!
If I may repeat what I'm hearing so far.
That infinity focus wide open, center frame, focus ring is back a tad from hardstop. However, focus wide open in the extreme corner requires focus toward the hardstop. From DavidBM.
This scenario suggests the field curvature is inward toward the edges as in holding an open umbrella out horizontally. This would be the opposite from a typical M mount lens, where the thick Sony filter stack's effect is equivalent to the wind blowing the umbrella out so as the umbrella is pointed away from the handle. And, to focus for the corners with a M mount lens on a Sony sensor, one would pull focus back from infinity.
Fred is saying that for optimum infinity sharpness, to focus midfield at shooting aperture. This would suggest that to sharpen up the extreme corners, one would focus toward the infinity hardstop (from center infinity focus as suggested above) and that focusing stopped down may flatten the extreme field curvature experienced wide open (and not just widen the depth of field). So, what I'm saying is that a smaller aperture flattens the field versus a depth of field benefit.
Am I on target here?
And one last comment on the lens review thus far; the lateral chromic aberations is so bad that when Lightroom takes the color out, the lack of sharpness in the structures is significant.
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