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02-09-2009, 06:44 PM   #316
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#9030263 from Willoughby's works. I images look good for now. Thought the MF was jacked, but pulled back on the focusing ring a little and now the MF works. Is anyone else's like this?

-Andy

02-13-2009, 06:31 PM   #317
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QuoteOriginally posted by cczona Quote
S/N 9029255 purchased 2/09 from Adorama. BAD.

Decentering right, which looks downright appalling by 36-50mm when it adds ghosting to the left side's blurring and yellow-blue CA. Front focuses at all focal lengths except 16mm and 50mm, which means it's not correctable in-camera.
It also sticks at 28mm, is stiff through 28-50, and (I don't think this has been mentioned before) the focus ring doesn't stop at either endpoint. It just experiences a momentary snag at minimum focus or infinity that feels similar to the bump at 28mm, then the ring goes right on turning around and around and around. I've never had a lens do this. Is it in somehow a feature?? If it's a defect, wow, it seems rather a significant omission.

Last edited by cczona; 02-13-2009 at 06:37 PM.
02-13-2009, 06:39 PM   #318
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QuoteOriginally posted by cczona Quote
the focus ring doesn't stop at either endpoint. It just experiences a momentary snag at minimum focus or infinity that feels similar to the bump at 28mm, then the ring goes right on turning around and around and around. I've never had a lens do this. Is it in somehow a feature??
Yes, it's normal for the focus ring to turn past the ends of the focusing "endpoint" or throw.

It surprised me at first, as well, but all 3 of my Pentax SDM lenses do this.

-Chris
02-13-2009, 09:42 PM   #319
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9019540

Great lens...first try. Tack sharp all around and I love the SDM!

02-14-2009, 06:14 AM   #320
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Increase your chances of getting a good copy?

Hi everybody,

I tried to find (with Bayes nets) some correlation between the SN and the probability of having a good copy of the DA*16-50, and the only valid explanation seem to be linked to the fourth digit.

Based on all the samples, there 65% random chance to get a good copy. But if the fourth digit is 0, 1 or 2 then the probability increases to 89%. The digit to check is the X as in 902X306. (of the 147 SN I checked, 37 have X <=2). I cannot find any correlation with the other digits.

I am not sure how statistically valid it is but I guess that if I had to buy this lens I would give it a try! Who knows why... perhaps this correspond to a plant, or workgroup, or an individual... or it is pure coincidence.

Cheers,
Grégoire
02-17-2009, 10:28 AM   #321
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9021887 - Good after servicing (back focus)

Hi everybody,

The title says all. I had a back focus problem with a K10D (bought in late June 2007), already slightly noticeable with the 18-55 kit lens and much more with the f/2.8 DA* 16-50 I bought in April 2008. I requested Pentax France to service the camera together with all its lenses and since then everything is fine.
02-19-2009, 03:38 PM   #322
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QuoteOriginally posted by frostugh Quote
I bought mine from Willoughby's Camera within the last month. The serial number is 9021232 and the edges are super sharp wide open at 16mm. Given the history with this lens, I've been looking for trouble with mine, but I haven't found anything yet.
Scratch that. With a month left on the warranty, I decided to send it in to Pentax because I wasn't happy with its overall sharpness. The gamble paid off; they sent a replacement (SN #9029330) which is definitely better. I love this lens even more now!
02-19-2009, 09:58 PM   #323
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I have 9027536. I am not sure if it is bad or not but my sigma 18-50 ex dc macro seems sharper. Also at 50mm f2.8 it seems to have pronounced vignetting. Is this normal? I expected tack sharp but I think it's okay. It certainly doesn't blow the socks off of the sigma. I only have one so if anyone lives near San Jose, CA I would love to compare lenses.

02-21-2009, 03:05 PM   #324
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Sn 9029956

Received yesterday from Amazon. Good news is that it doesn't appear as though this copy was previously returned to Amazon from someone in this forum. Since I'm rather new at this, to my untrained eye, the lens appears to be good, but I would hate to find out 6 months or a year from now that my copy wasn't any good.

How do these pictures look?

Pentax DA* 16-50mm test - a set on Flickr

Thanks!
02-22-2009, 09:00 PM   #325
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Is there a single list of serial numbers out there for good/bad?
02-22-2009, 09:08 PM   #326
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QuoteOriginally posted by lawsonstone Quote
Is there a single list of serial numbers out there for good/bad?
I'd pm le_roi_ponpon - it looks like he's run a statistical analysis of some sort on this info. (several posts up the thread)
03-04-2009, 12:05 AM   #327
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9030087 Good!
03-05-2009, 06:42 PM   #328
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whats an easy way to test my 16-50mm lens

Can someone refer to the link that describes how to tell if I have a good 16-50 lens or a dud.
Thanks
03-06-2009, 08:14 PM   #329
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QuoteOriginally posted by aegisphan Quote
It either has back or front focus, coupling with the very noticeable softness at wide open.
Hi, here's the simple version.

hth
03-06-2009, 08:16 PM   #330
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QuoteOriginally posted by alib99 Quote
If you do not know if it is bad then I guess it is a good copy
And also this...
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