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07-24-2007, 08:17 PM   #1
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Autofocus issues wide angle on K10d

Anyone else having AF issues on wide angel shots with K10D? I can't seem to AF accurately @ 18mm on K10d, tried 2 lenses already but once I zoom in further autofocus backs up a bit. When I try manual focus a VERY wide range of focus is considered "in focus"

07-25-2007, 01:51 AM   #2
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Not really understanding your question. At 18mm focus should be easy as there will be a very wide depth of field. this is also why you are getting a wide lattitude from the green focus indicator.

When you "zoom in a bit" you need to refocus as well.
07-25-2007, 05:16 AM   #3
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Now that you bring this up, my K10D ocassionally also encounters trouble when trying to focus with my 12-24mm, but only for distant subjects. When I press the shutter button halfway down, the AF system doesn't always recognize that the subject is already in focus (usually landscape), and the camera tries to move the focusing ring further to the left than it will go.

Is this normal, or should I get the AF system checked? It might also be the lens's fault, since the AF works perfectly with my tele lenses.

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07-25-2007, 05:52 AM   #4
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QuoteOriginally posted by Mo Quote
Now that you bring this up, my K10D ocassionally also encounters trouble when trying to focus with my 12-24mm, but only for distant subjects. When I press the shutter button halfway down, the AF system doesn't always recognize that the subject is already in focus (usually landscape), and the camera tries to move the focusing ring further to the left than it will go.

Is this normal, or should I get the AF system checked? It might also be the lens's fault, since the AF works perfectly with my tele lenses.
Adam, this is exactly what my FA20/2.8 would do. It was like it was hitting the stopping screw before it reached full infinity focus. I had the infinity focus point adjusted (on the lens) and now it works fine.

07-25-2007, 06:42 AM   #5
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QuoteOriginally posted by timmciglobal Quote
Anyone else having AF issues on wide angel shots with K10D? I can't seem to AF accurately @ 18mm on K10d, tried 2 lenses already but once I zoom in further autofocus backs up a bit. When I try manual focus a VERY wide range of focus is considered "in focus"
Precise AF with super wide lens will require precise and high resolution AF sensor which the K10D lacks. It is just because the image details has far little magnification and just the AF sensor need to have more pixel in it, in order to minimize the errors and thus give more accurate results.

As such, the AF is just a hit and miss with AF system with insufficient resolving power.

As for other who suggests to relief the infinity focus tolerance to adapt the body. This will only allow the AF system to release the shutter in the single AF mode but actually it can't help to make more accurately focused photos.

So, which Pentax body is capable of more accurate focus with wide lenses? My answer is the MZ-S but it is not a DSLR anyway. The good thing is that Pentax CAN actually do it but whether they will put that good stuff in a DSLR is something that we still need to wait.
07-25-2007, 09:29 AM   #6
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Perhaps the OP can post some wide angle shots that he considers are out of focus. I have not had this problem.

Is it that your shots are out of focus or that the autofocus "hunts" for focus but cant achieve it?
07-25-2007, 11:50 AM   #7
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I don't have the answer to this problem but I notice the same tendency with my DA16-45/4 too on the DS at 16mm. Often the DS tried to AF a little further than it should. Tried it on another body K100D with identical behaviour. However, my old pair of Z-1p were spot on. I can only imagine the AF module of Pentax DSLRs must be made with some compromises (cost cutting maybe). As to the DOF of wide angles and the practice of hyperfocal, my own finding is that even if the subjects were well covered within the DOF, the difference in detail is obvious for what's actually in focus when viewing on the monitor at 100%. I always get sharper images focus at 45mm then zoom out to shoot than focus at 16mm (almost impossible to manual focus with such wide angle).
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