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12-07-2010, 05:21 AM   #1
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AF adjustment not enough??

Hey all, just got a K-5 and definitely an awesome camera! I also have a tamron 17-50mm 2.8 (which I also love), but noticed that it still front focuses slightly despite an aggressive -10 AF adjustment. Is there a way to do more than -10 (maybe need like -15 or something)? I'd hate to have to rely on LV AF everytime I want to use F2.8 with this lens

12-07-2010, 05:53 AM   #2
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Until someone comes out with a way to use Debug mode (as I do on the K20D for such problems) you won't be making more than the -10 adjusment.
12-07-2010, 06:40 AM   #3
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You'll need to send the equipment for calibration. I don't know if Pentax will work on 3rd party equipment though, so you might need to find an independent shop that will do it for you.
12-07-2010, 10:52 AM   #4
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You may want to check the Tamron lens on another body...

I have the same one and it front focuses beyond what my K5 can correct (all other lenses are dead sharp with no adjustment). The same lens is unusable on my K100d and is barely usable at maximum adjustment on my K20d.

I'll be sending in the Tamron for warranty work after the holidays.

Pat

12-07-2010, 02:32 PM   #5
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it seemed to AF with very very little correction on my KX, But for some reason, not so well on my K5.
Maybe has something to do with the greater resolution on the K5?
12-07-2010, 02:34 PM   #6
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Have you tried other lenses on the K5?
12-07-2010, 02:37 PM   #7
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QuoteOriginally posted by ueda_masaki Quote
it seemed to AF with very very little correction on my KX, But for some reason, not so well on my K5.
Maybe has something to do with the greater resolution on the K5?
The best comparison I found to see how well the fine adjustments were working was to first take the photo in LV (live view) using contrast focus and then switch off LV to take the photo using the phase focus method.

From what I have learned, the phase focus is calibrated the contrast focus method (which is more accurate) and using the fine adjustments, you can tune the focus in closer to the contrast focus.

See this thread: https://www.pentaxforums.com/forums/pentax-k-5-forum/123036-phase-detect-auto...naccurate.html
12-07-2010, 02:38 PM   #8
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yeah, that's how I've been doing it and noticed the FF. photos are definitely sharper in LV every time vs my current -10 AF adjustment in normal AF

12-07-2010, 04:16 PM   #9
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Does the Tamron FF as much at both long and short ends of the zoom?

Do you have other lenses? Try them out. If they all need negative adjustment maybe it's the body that needs adjustment. Otherwise, your Tamron probably needs recalibrating.

Oh, I just thought of something. I believe there's a "universal" focus adjustment as well as lens-specific ones. Maybe you could adjust the "universal adjustment to say -5. This might give you enough adjustment room for the Tamron. Then you would just have to add +5 to all your other lenses to compensate (and hope they don't run out of adjustment).

This would probably only be a short-term fix though. I'd get the Tamron recalibrated.
12-08-2010, 02:16 AM   #10
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QuoteOriginally posted by ueda_masaki Quote
I also have a tamron 17-50mm 2.8 (which I also love), but noticed that it still front focuses slightly despite an aggressive -10 AF adjustment.
After several copies the last Tamron 17-50 did the same on my K-5. Even after -10 AF adjustment it still front focused by approx. 10 cm. I just returned it (and since I got fed up after trying several bad copies, all with different type of issues, I just purchased DA* 16-50 which just works right out of the box).
12-08-2010, 05:32 PM   #11
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yeah, it's a shame that there's so many FF/BF problems with the tammy. It was fantastic with my K-x, but is a bit off on my K-5. Other lenses are pretty good on the K-5 too. I might just wait until someone finds out how to get the debug working, cuz I got my tammy gray market and sending it in would be a hassle.
12-08-2010, 05:33 PM   #12
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QuoteOriginally posted by secateurs Quote
Oh, I just thought of something. I believe there's a "universal" focus adjustment as well as lens-specific ones. Maybe you could adjust the "universal adjustment to say -5. This might give you enough adjustment room for the Tamron. Then you would just have to add +5 to all your other lenses to compensate (and hope they don't run out of adjustment).

This would probably only be a short-term fix though. I'd get the Tamron recalibrated.
I don't think the universal focus stacks with the lens-specific one. (unfortunately!)
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