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08-24-2022, 11:53 AM   #1
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K3 III AF Adjustment anomalies

Hello Guys !

I was a little bit reluctant to make this topic but i'm deep into the woods regarding thins "issue" and would like to hear about your opinion on this topic.The thing is that before this machine with the K3 anf K5 it was an easy choice and a very much convenient way to do the AF Adjusment of my 16-50 and 50-135 lenses. I just calibrated them to be good at their higher ends "50 and 135" at F2.8 with the central focusing point.
Now with the K3 III i noticed that if i calibrate the lenses to their best with the single center point method then after choosing the best, the grouped modes are not giving the sharpest images. I have to confess that for me that calibrating with the single center focus point the sharpest images are almost front focused ones.
Now if i use this method then a way less ideal AF Adjustment setting for example like 0 or +4 instead of +5 or +7 are working way better with the grouped, automatic focusing.

So for example, calibrating with the center point and using that is doing great images all of them with AF Adjusment setting +5 , then using the more intelligent focusing the pictures are way better with AF +4, or even the defauilt 0 setting.

What are your opinion on it ?

Best Regards,
Levente

08-24-2022, 04:54 PM   #2
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QuoteOriginally posted by Levus Quote
then using the more intelligent focusing the pictures are way better with AF +4, or even the defauilt 0 setting.
More intelligent ? The camera has no idea where you want the focus point to be. It is not at all intelligent. Use single point and you tell the camera where you want focus to be.
08-24-2022, 09:46 PM   #3
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That is more ore less one additional effect of my experience:

Can someone check the accuracy/difference of all AF points in AF-S Select - PentaxForums.com

Since this, I'm only using this "intelligent" group AF things with smaller aperture than the maximum opening.
08-24-2022, 11:30 PM   #4
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I recall my friends using a Canon and Nikon DSLR some years ago saying that the outer AF points weren't accurate and that they used the center point when AF accuracy was required.

08-25-2022, 12:54 AM   #5
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QuoteOriginally posted by pschlute Quote
More intelligent ? The camera has no idea where you want the focus point to be. It is not at all intelligent. Use single point and you tell the camera where you want focus to be.
You're right, bad choice of word on my part. I only wanted to say that if i use the zone modes, then the precisely choosed AF adjustment value what i got when calibrating against the center point, should be lowered to have the best results.
08-25-2022, 03:56 AM   #6
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How to optimize focusing accuracy with large-aperture lenses / explore | RICOH IMAGING

This links to the Pentax advise page regarding achieving best focus and af adjustment.
08-25-2022, 04:29 AM - 1 Like   #7
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I've noticed all my lenses struggle to get ideal focus in auto modes in relatively poor or flat light when wide open. So I mostly use zone and smaller aperture in such circumstances.
No issues in good light.

08-29-2022, 03:18 PM   #8
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I have found, especially with my 50-135, focus calibration to be difficult at best. It's not at all consistent at the various outer points making tracking mostly useless, and I find that calibrating the lens at one distance means it's out at another. Add to that that LV focus is never particularly sharp (worse than OVF) and its overall quite frustrating. I sacrificed some features to stick with Pentax so I wouldn't have to re-buy lenses, but now I'm stuck trying to make the best of this questionable combination.
08-29-2022, 05:13 PM   #9
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QuoteOriginally posted by sebberry Quote
I have found, especially with my 50-135, focus calibration to be difficult at best. It's not at all consistent at the various outer points making tracking mostly useless, and I find that calibrating the lens at one distance means it's out at another. Add to that that LV focus is never particularly sharp (worse than OVF) and its overall quite frustrating. I sacrificed some features to stick with Pentax so I wouldn't have to re-buy lenses, but now I'm stuck trying to make the best of this questionable combination.
I have no problems with my 50-135, Seberry.

You haven't said that you did a decentreing test when you first purchased?
09-04-2022, 08:13 PM   #10
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QuoteOriginally posted by clackers Quote
I have no problems with my 50-135, Seberry.

You haven't said that you did a decentreing test when you first purchased?
No, I didn't. That would have probably been about 10 years and 3 SDM motors ago...

Why would it FF considerably during LV? Why is the FF/BF in OVF inconsistent? Why when focusing on objects closer to the lens, it produces a lovely sharp image, but objects further away are a guessing game as to whether they'll be in focus? It's a beautiful lens, but Pentax AF in general continues to leave lots to be desired.
09-05-2022, 01:32 PM   #11
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Firmware version? Have you tried resetting after setting the Fine focus back to zero?
09-05-2022, 04:46 PM - 1 Like   #12
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QuoteOriginally posted by sebberry Quote
No, I didn't. That would have probably been about 10 years and 3 SDM motors ago...

Why would it FF considerably during LV? Why is the FF/BF in OVF inconsistent? Why when focusing on objects closer to the lens, it produces a lovely sharp image, but objects further away are a guessing game as to whether they'll be in focus? It's a beautiful lens, but Pentax AF in general continues to leave lots to be desired.
Yeah, I would really do the decentreing test again, it may have taken a fall or knock in the decade, even one you weren't aware of .... Clackers' Beginners Tip 18: Testing Lenses for Decentering - PentaxForums.com
09-12-2022, 01:10 AM   #13
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The critical point for fine-tuning any lens is at the widest aperture and the shortest distance from the subject. It is when there is less depth of field and therefore the adjustment is more sensitive. In a zoom this point is at its greatest focal length, at maximum aperture and at the minimum focus distance stated in the specifications. Calibrating the focus well at this point, which is the most demanding for the lens, the rest should not give you problems. Cordial greetings!

Last edited by Sandy Hancock; 09-12-2022 at 01:24 AM. Reason: Translated
09-12-2022, 04:35 AM - 2 Likes   #14
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There is no issue there. Just calibrate your lenses-K-3iii to accurately focus when using the single center AF point at the widest aperture of your lenses. When you use the combo in single focus mode and centre point AF you'll get the expected results. Use the group modes only for AF-C when you try to focus on anything moving and you will also get excellent results. Use the right settings for any given situation and enjoy shooting your K-3iii!
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