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08-07-2016, 06:35 PM   #1
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K-1 AF viewfinder problem

I am having problem with the AF on the viewfinder with the 28-105mm
when the lens is extended after about 80mm.
I am using point focus.
I reset all the setup with no success.
AF works fine in liveview
I think the problem came when I update the firmware to 1.20.
Any suggestions?
Thank for your help

08-07-2016, 06:52 PM   #2
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May not mean a thing but did you read the thread https://www.pentaxforums.com/forums/190-pentax-k-1/327333-strange-af-issue-da-300-a.html?
08-07-2016, 07:05 PM   #3
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Original Poster
AF problem

Yes I read this thread, I did what it is recommended with no success.
08-07-2016, 08:07 PM   #4
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I don't own either the K-1 or the D FA 28-105, but I will ask the standard hard questions:
  • What do you mean by problem? Does the camera not attempt AF? Is it unable to attain focus? Is focus inaccurate? Something else?
  • Do you have problems with PDAF (viewfinder AF) with any other lens?
  • Have you been able to test your 28-105 on another Pentax body?
...and lastly...Both camera and lens are still under warranty. Have you been in conversation with Ricoh/Pentax? If either lens or camera is less than a month old, have you been in conversation with your dealer to arrange for possible exchange?


Steve


Last edited by stevebrot; 08-07-2016 at 08:15 PM.
08-07-2016, 10:16 PM   #5
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I think K-1 users may refer to this issue as "PDAF Freezing", because the lens doesn't move at all, but the AF signal is flickering.
From all my observations and personal experiences I speculate that this issue attributes to Pentax's SDM design deficiency which cannot be handled well by K-1.

The reason: My DFA 24-70 (a Tamron rebadge SDM, you guys all kown) is clearly free of such issue. But DA* 300 and DFA 28-105 (mentioned by the original poster) both use Pentax's own SDM, which does not own a good reputation among Pentaxians.
Now that the "PDAF Freezing" issue can be solved by switching to CDAF, I hope this issue can be setteled by a future firmware release. I will add this point to the pinned thread.
08-07-2016, 10:55 PM   #6
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QuoteOriginally posted by Grognard Quote
But DA* 300 and DFA 28-105 (mentioned by the original poster) both use Pentax's own SDM
It is very short cut to a conclusion. What I know for sure is that the DFA150-450 and DFA70-200 supposedly Ricoh design (like DFA28-105) have totally different SDM designs, there is no comparison with "old" DA300 SDM, I don't know about the DFA28-105.
08-08-2016, 01:06 AM   #7
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The D FA 28-105 doesn't use a SDM motor at all - it's using a DC motor. But I'm not sure if the difference is relevant in this case.
08-08-2016, 04:58 AM   #8
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QuoteOriginally posted by gerardbaron Quote
I am having problem with the AF on the viewfinder with the 28-105mm
when the lens is extended after about 80mm.
I am using point focus.
I reset all the setup with no success.
AF works fine in liveview
I think the problem came when I update the firmware to 1.20.
Any suggestions?
Thank for your help
I've had no problem with this combination, and am on 1.20.

08-08-2016, 12:10 PM   #9
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Original Poster
QuoteOriginally posted by gerardbaron Quote
I am having problem with the AF on the viewfinder with the 28-105mm
when the lens is extended after about 80mm.
I am using point focus.
I reset all the setup with no success.
AF works fine in liveview
I think the problem came when I update the firmware to 1.20.
Any suggestions?
Thank for your help
I try the FA 28-105mm on a K-5: same problem
I mount another lens on the K-1. AF works like a charm
So I decide to return the lens and exchange it for a new one 20-105mm same lens.
The new lens works perfectly.
Problem solved.
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