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08-27-2013, 02:06 PM   #1
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DA*55 autofocus accuracy

I tried several copies of this lens on a K-7 and one copy on a K-5 a few years ago and found the AF to be extremely erratic. In addition, it had a huge backfocus problem that was difficult to correct even with maximum microadjustment. I wonder if these issues persist with newer copies of the DA*55, especially on a K-5. Also, how is the SDM holding up?

Rob

08-27-2013, 02:09 PM   #2
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QuoteOriginally posted by robgo2 Quote
I tried several copies of this lens on a K-7 and one copy on a K-5 a few years ago and found the AF to be extremely erratic. In addition, it had a huge backfocus problem that was difficult to correct even with maximum microadjustment. I wonder if these issues persist with newer copies of the DA*55, especially on a K-5. Also, how is the SDM holding up?

Rob
I have had a copy for 3 years now and the SDM is fine.

My understanding is that on the K5 II any erratic behavior of the DA *55 is gone. I don't have significant issues on my K5, but that doesn't say anything about more recent copies...
09-02-2013, 07:40 AM   #3
sTi
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I tried 3 copies simultaneously on my K-5. Two were focussing erratically and I sent them back. The third worked perfectly on the K-5 and does so as well on my K-5 II. So I think it's just a matter of getting a good copy, then you will have no problems, so make sure to buy from a reputable dealer where you can return defective items without hassle.
Interestingly, of the three copies I tried the flawless one had the newest serial nr. and was also the only one that included a small notice in the packaging that Pentax is now a Ricoh Company
09-02-2013, 08:37 AM   #4
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QuoteOriginally posted by sTi Quote
I tried 3 copies simultaneously on my K-5. Two were focussing erratically and I sent them back. The third worked perfectly on the K-5 and does so as well on my K-5 II. So I think it's just a matter of getting a good copy, then you will have no problems, so make sure to buy from a reputable dealer where you can return defective items without hassle.
Interestingly, of the three copies I tried the flawless one had the newest serial nr. and was also the only one that included a small notice in the packaging that Pentax is now a Ricoh Company
Believe it or not, I tested a total of 5 copies before giving up.

Rob

09-02-2013, 10:47 AM   #5
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You said "a few years ago", so maybe before the re-introduction of quality control under Ricoh?
I am only half-joking, actually. Almost all the stuff I bought (also a few years ago) when Hoya was running the show I had to send in for calibration or repair, whereas my Pentax purchases during the last year have been working perfectly right out of the box, so at least from my (limited) experience I would guess the chances could be much lower now to get mis- (or more likely non-) calibrated gear when buying new.
09-02-2013, 11:04 AM   #6
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Mine requires a +10 adjustment on my K-5. Fairly please with the results after that adjustment though.
09-02-2013, 12:27 PM   #7
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QuoteOriginally posted by sTi Quote
You said "a few years ago", so maybe before the re-introduction of quality control under Ricoh?
I am only half-joking, actually. Almost all the stuff I bought (also a few years ago) when Hoya was running the show I had to send in for calibration or repair, whereas my Pentax purchases during the last year have been working perfectly right out of the box, so at least from my (limited) experience I would guess the chances could be much lower now to get mis- (or more likely non-) calibrated gear when buying new.
I don't know if it was a quality control or a design issue. I only know that I could not get a copy of the DA*55 that would focus accurately on a consistent basis. It was like rolling dice. It's worth noting that when DPreview tested the lens in 2009, they found the same erratic behavior, which they attributed to tilting of the plane of focus, i.e. it was a problem with the optical construction rather than with the focusing mechanism itself, although the two are closely related. I have no idea whether Pentax has rectified the problem since that time.

Rob
09-02-2013, 11:09 PM   #8
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Dunno if it's Pentax quality issues or what. I have understood that Pentax had some trouble with Vietnam plant QC and then some under Hoya?

Either way, I have a copy of 55mm and while otherwise a good lens, the focus is just what The Internet tells, it's sometimes there and sometimes here.. my most erratic lens. About +5 AF fine tuning needed (all my lenses needed +2..+8, mostly K-7 body error that is).

One thing I noted; most of my Pentax lenses have to be adjusted (body AF fine tune I mean) so that the DOF is mostly behind the subject. Maybe 3/4 back, 1/4 front of subject. Doing so results in most infinity sharpness. Google also tells that more of the DoF is supposed to be behind the subject anyway, with normal shooting distances. Just saying that if one sets DoF to be equal front and back, some infinity focus sharpness might be lost.

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