Originally posted by stevebrot AF on my K-3 works just fine with my copy of the FA 77/1.8, meaning that it is fast and accurate. My use of manual focus reflects my choice of subjects and work flow and is not an indication that there is a problem, only that manual focus is the better choice.
It would be helpful to know how are you determining the need for AF fine adjust and what is your process.
I must apologize for a bit of misdirection in my comment above.
The suggestion of field curvature being a possible explanation was off base and I will correct my comment above. Field curvature would show itself as peripheral aspects of a flat subject showing front focus (forward of the intended plane of focus) when the point of focus was placed at the center of the frame. This happens with both manual and auto focus. In the same situation, but with point of focus placed away from center, the center aspect of the frame will show back focus (behind the intended plane of focus).
The fine adjustment will affect all of the focus points the same and all should have the same relative accuracy as the center point. This will be the case regardless of any field curvature that may be present. In other words, field curvature should not effect the ability to attain accurate focus
per se.
Steve
shooting at a front lit flat target ~6 meters away, at f1.8, viewing the results on an iPad at 100%, around 10 shots to determine hit rate.
Then going outside and shooting a subject about the same distance and looking at the eyes and eyelashes. At that distance there's enough DoF that both should still be in focus if the focus is properly set.
edit: more tests (all lenses wide open)
K-1 II + 77mm: all focus points works
K-1 II + 50mm 1.4 SDM: all focus points works
K-1 II + Sigma 85mm 1.4: some focus points more accurate than others
K-3 II + 50mm 1.4 SDM: all focus points works
K-3 II + 77mm: center 3 focus points and rest of points differ
K-3 II + Sigma 85mm 1.4: all focus point works
And this is why I'm dipping my toes in mirrorless
btw, either I got the sharpest 50mm SDM ever, or the worst 3 16-50mms ever, but the 50mm at 1.4 is sharper or about equal to the 16-50mm at f4, and looks to be better than the 55mm SDM at f2. the lens is amazing. I'm wondering why the Tokina Opera version isn't as popular (as in, not popular at all based on the support raw processing software has given it)