My K-5 has a serious Back Focus issue with ALL my auto-focus lenses, but not with my manual focus lenses.
It doesn't make sense: With both types of lenses, the same phase-detection system is used.
* When I use a MF lens (A* 2.8 300mm or A 1.7 50mm), the focus detection (using the center AF point) is spot-on with zero AF correction.
* When I use a AF lens (DA 18-135 WR, DA* 16-50, DA 1.8 50 AL, DA 2.4 35 AL, FA 2.0 35), the focus consistently needs about +160-170µm correction (I use the DEBUG mode for this, because the normal "C.26 AF Fine Adjustment" isn't going far enough).
I check the focus both using a Katzeye split prism focusing screen and by manifying the recorded images. I've taken 100s of test images, both on flat high- and low-contrast targets (such as a printed test sheet and printed colored images). Always at max aperture. The result is consistent.
Even comparing the DA 50/1.8 to the A 50/1.7, both having nearly the same wide aperture, and same focal length, their phase-detection AF is 160µm apart. How can this be? And can this be fixed?
Has anyone else seen something like this?
Oh, I forgot to point out that I see this issue only with my K-5 but not with my K-3: There, both types of lenses are spot-on. So it's not a lens issue in itself, but maybe something related to the K-5 handling MF lenses differently in phase-detection focusing (why, though?).
Last edited by tempelorg; 06-30-2014 at 08:14 AM.
Reason: adds note that K-3 doesn't show this issue