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12-23-2012, 06:53 AM   #1
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DA* 50 back focus - ways to resolve?

Hi all,

My DA*50 has serious back focus and in camera adjustment to the max still can't bring it back. At f/1.6 it can be tolerate but at f/1.4 it still back focus.
I am thinking:
1. Send to Pentax to fix? anyone has experience?
2. Send it back to seller (lose some shipping and re-stocking fee)?

Would you suggest anything else?

Thanks,
Lee

12-23-2012, 07:45 AM   #2
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Hi there, not sure whether you mean the da*16-50 or the da*55 or the new plastic da 50. I don't think there is a straight da*50.
Either way that probably doesn't matter. What does matter is whether you are mounting it on your k5 (you don't say) or the k200. I know with the K5 that you can download a great programme called pktether which amongst other things allows you a broader range of front a back focus adjustment as it gives you the ability to enter 'debug mode'. And just for the sake of time I'm going to presume you haven't used pktether to solve the issue but forgive me if you have.

My fa77 needed more than +10 so I use debug mode to shift the middle zero point of fine focus adjust to a new value of +5. Essentially my scale now goes -5 to +15 and my 77 sits pretty at +12 with all my other lenses in the low pluses.
There's more to explain about debug than just that but there's plenty of info out there on how to use it and it's very simple.

Last edited by London Rob; 12-23-2012 at 07:48 AM. Reason: more info
12-23-2012, 10:55 AM   #3
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@London Rob: interesting. I have not heard of shifting the center point . Do you have a link? I am just curious.

BTW to the OP, I sent my K5 in (without lenses) and asked that they adjust the calibration because all my lenses needed + adjustments (some > 10) and they did a great job at CRIS. I don't need any adjustments on my lenses except a +4 on my DA*55.
12-23-2012, 02:38 PM   #4
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MY understanding is that debug mode in the easily searchable pktether allows you to do this: You can access what seems to be an engineer only menu, one of these governs af adjust and within this there is a similar -/+ adjust to the K5's regular focus tweaking feature. BUT this has increments of 10 so goes up to 100 in 10 steps. MY understanding is that 10 in debug=1 in regular. It is a global body adjustment and does not recognise lenses.

So as I needed more than +10 in regular, I adjust debug to +50 (+5 in real money) and set. This appears based on testing and the opinion of many others to re-assign the zero point in regular to a permanent +5. It doesn't show as this it still reads 0 but my lens now comes to life at +7 (+12), all my other lenses also hit their sweet spots at a different figure in relation to my 5 step shift.

you have to watch if any of you lenses needed big minus changes, as you now have in the real world nothing more than -5 available as you have shifted the whole thing 5 steps to the right.

Phew ! I think I'm right.

12-23-2012, 09:46 PM   #5
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London Rob: good to know. Thanks for sharing. Hopefully I won't need it anytime soon.
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