K-01 and K5-II Contrast AF problems

Started May 5, 2013 | Discussions thread
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philzucker
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K-01 and K5-II Contrast AF problems
May 5, 2013

Yesterday my K-01 arrived, and of course I went around trying it out. More about that later ...

I was quite thrilled with the first results, but I also noticed some softness using my Tamron 18-250 at its long end and started some testing today. During those tests I switched from the 18-250 to my Tamron 70-200/2.8 to do the testing with a better quality lens and then also included my K5-II body. I used a tripod and a wireless remote, of course, ISO 100 and Av mode. The results were more or less the same and - IMO - somewhat disconcerting:

- Contrast AF didn't work well with either the 18-250@250mm or the 70-200@200mm. I tried a variety of subjects with different amounts of contrast with more or less the same results.

- manual AF on the K-01 and PD-AF on the K5-II worked flawlessly and accurate ...

Here one of the many example I shot that demonstrate my findings best - all samples imported in LR 4.4, cropped and slightly exposure adjusted, no other modifications - and of course these are 100% crops if you see them at original size. What you're looking it is a newspaper pinned to a garden shed positioned around 10 meters from the camera:

K-01 with Tamron 70-200@200mm, Contrast AF

K-01, same lens, manual focus - focus peaking used

K5-II, same lens, Contrast AF

K5-II, same lens, phase detection AF

I had more or less the same results with the Tamron 18-250@250mm - flawless focus on the K5-II with PD-AF, out of focus pictures using Contrast-AF on both bodies.

Have to add that I also tested with other lenses. For example with the FA35/2.0 - hadn't too many problems with it at varying distances. In one setup I found some very slight front focusing with the K5-II and PD-AF, perfect focus with K5-II and Contrast AF and slight back focusing with the K-01's Contrast AF, but I can live with all that.

What bugs me is the inability of both bodies to focus correctly with Contrast AF using my two telephoto lenses at its long ends ... What is happening here? What am I doing wrong? Or what are the bodies doing wrong? Am I expecting too much out of Contrast AF? Has anybody had comparable experiences?

Have to stress again that I did the testing with lots of different subjects at different distances and that I do sincerely hope that I was careful enough to rule out user errors (like tripod shake etc.). As I used the wireless remote sensor stabilization was automatically turned off with both bodies. And I took multiple shots too. So these results should really be valid ...

Any thoughts and help on this much appreciated!

Phil

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Pentax K-01 Pentax K-5
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