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05-20-2010, 04:17 PM   #1
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Bad lenses - how often do they happen?

I have just recently posted a note about my experience with a bad Pentax DA 10-17mm lens – it is now on its way for exchange to the dealer I bought it from.
This experience was for me quite an eye opener as after over 30 years of using SLR and lately DSLR cameras (last 20 years exclusively Pentax), I never had a problem with any lens. And I have purchased/sold over all these years many second hand lenses, mind you mostly manual focus primes, and it never occurred to me that as long as the glass is perfectly clear, something could go wrong with the lens. Now I see that at 63 I should have been less na´ve and maybe more educated….

So, I started reading this SLR lens forum with the focus on bad lenses, and it looks like some kind of “misalignment and a little defect here and there” is fairly frequent, especially with the new high-tech lenses. As I am just considering to buy almost a new Pentax lens from a member of this forum, it makes me think seriously about warranty, even so that the lens in question is evidently in a good shape.

One must wonder as well, how representative/objective are all these lens evaluations and comparisons, considering that a tested lens might have a “little defect” making it perform and have an IQ worse than the same lens in an optimum/perfect condition. How can you tell that a lens you are testing is truly a perfect copy?!
Is there any consensus on this issue?


Last edited by luma; 05-20-2010 at 04:21 PM. Reason: misspelled
05-20-2010, 04:25 PM   #2
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I don't think there is any consensus. Half of it is just speculation, while the other half is that some lenses indeed to have defects. The most common occurrence of this is with the DA* 16-50mm, although those have started looking much better lately.

Of all my lenses, I think I've only seen defects in two (thats about 1%). Furthermore, no new lens has ever shown any signs of trouble. I guess if you want to stay 100% sure that everything is OK, though, just stick with the older glass

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05-20-2010, 04:50 PM   #3
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Being an end user only I have no idea what % of new lenses being sold have some kind of defects, but I feel they are more frequent these days since everyone is trying to cut cost for max profit. I have purchased my share of defective lenses in recent years. Whether my lenses are perfectly aligned I have no way to test. If they are equally sharp (or blurry) on both sides, then practically good enough for me. My DA10-17 is fine btw, though high on CA.
05-20-2010, 05:03 PM   #4
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S*** happens.

If you knew the percentages of faulty lenses for each model, would it change your buying pattern?

It's not worth worrying about. True lemons are rare, and if you based your lens acquisitions out of fear of this, you would never wind up buying anything.

05-20-2010, 05:44 PM   #5
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Well, you are right, a fear of lemons should not prevent one from buying a NEW lens, where you have a waranty of free repair/exchange, iregardless how inconvenient it might be. Problems usually show up in first few months and you can deal with it.
What I am talking here about are used lenses, which grew in complexity so much that they simply do not last a generation any more...
05-21-2010, 08:30 AM   #6
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I have been very fortunate and through the years, I haven't ever had a defective lens. I will also add that most of my glass was purchased used and I haven't had issues with used glass either. I think your experience with the 10-17 was rare. There have been a lot of complaints with the newer SDM lenses and AF failures and I would hesitate to purchase a used one. I have no complaints about the focus of any lens I own although I don't take pictures of brick walls and try to look for flaws.
05-21-2010, 08:52 AM   #7
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QuoteOriginally posted by wlachan Quote
Being an end user only I have no idea what % of new lenses being sold have some kind of defects, but I feel they are more frequent these days since everyone is trying to cut cost for max profit. I have purchased my share of defective lenses in recent years.
(...)
Quality standards has probably gone down over the years, but I think much of the "problem" is the very complex designs of todays lenses, especially the faster zooms with internal zoom and focus. This compared with the ability to test lenses easy, and share the results and opinions on the Internet, is probably the reason why many newer lenses are prone to problems (and we acutally hear about it).
It was a lot simpler when the lens formulas consisted of not too many elements "stuffed" into a tube, focussing by helicoid.
05-21-2010, 09:38 AM   #8
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Another factor is how easy it is now to study every pixel of a shot and hunt for any imperfections. In the film days, people rarely blew up prints to 16x20 and poured over them with a loop. That's the equivalent of what we can do today with every shot we take, so any corner softness, or aberrations or whatever are much easier to find these days.

I agree with the other comments here (and probably your assertion too) that newer lenses are more complex and therefore more prone to break. I've been lucky with my new lenses (including several DA* lenses with SDM), but then I've only owned them for a couple of years. I'd be pleasantly surprised if they lasted 30 years or more without some service.

05-21-2010, 09:52 AM   #9
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I will say this: I am glad that defective/miscalibrated/decentered lenses occur more frequently than, say, defective/miscalibrated/decentered razor blade cartridges. A bad lens won't (usually) peel off my face!
05-21-2010, 10:11 AM   #10
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Manufacturers face several challenges, especially those who are making DSLR cameras using legacy registration distances.
The complexities of making retrofocal lenses, especially the very short ones is quite a challenge and auto focus requires more mechanical slop than manual focus.
Add to that, people are no longer willing to pay for quality control but are more than happy to blow their images up to several feet in length to inspect every single pixel with the intention of braying like donkeys when they find the slightest optical flaw.
There are probably more defective lenses hitting the stores now than there were when there were no zoom lenses, no AF lenses and every lens was individually collimated before it left the factory, but I suspect that there are a lot fewer bad lenses than one would think if one reads internet forums for information on the subject.
05-21-2010, 10:12 AM   #11
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I have only purchased 11 lenses new. Of those 11, two had defects that were readily apparent and that required a return for replacement:
  • Tamron 28/2.5 (02B) -- sticky aperture diaphragm
  • KMZ MC Zenitar 16/2.8 FE -- multiple mechanical issues...nothing worked properly
The Tamron was purchased in 1982 and the Zenitar about two years ago. What does this say about the state of lens QA? Virtually nothing. Much has changed since the Tamron was purchased and expectations are low for Russian products. Of the nine lenses that were problem free, seven were recent purchases.

Summary:

One out of eight recent purchases bad with that lens coming from Russia.


Steve


P.S. While not referring to lenses specifically, Consumer Reports publishes defect rates of 3-5% across the board for digital cameras. I would be very surprised if the data were significantly different for lenses.
05-21-2010, 10:20 AM   #12
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QuoteOriginally posted by rfortson Quote
Another factor is how easy it is now to study every pixel of a shot and hunt for any imperfections. In the film days, people rarely blew up prints to 16x20 and poured over them with a loop. That's the equivalent of what we can do today with every shot we take, so any corner softness, or aberrations or whatever are much easier to find these days.
I definitely agree with this - looking back at my old film shots, I'm sometimes surprised with how much missed focus or poor contrast I put up with in those days compared to digital these days. Digital essentially allows people to put a loupe up to all of their images, all of the time - back then, if it looked good at the print size I ended up with, I was perfectly happy with the photo. Now, even if the only destination is the web, sometimes there's still a little twinge of disappointment if it doesn't look great at 100% mag.
05-21-2010, 10:36 AM   #13
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I saw a DA* 200 with a cracked front element in a Yodobashi Camera some months ago and tried it to see how was it. The shots were sharp and nice. "Decentering" and some other symptoms are more often than not user related problems. The focusing motor failures is another story which I'm not going to talk about.
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