[jthommo]

Over in the other place a poll of SDM lens failures makes unedifying reading; the results so far:

16-50: 17 failures from 49.

50-135: 13 failures from 67.

17-70: One failure from eight.

200: One from 10.

300: One from 18.

60-250: all good from 13 so far.

55: Seven good copies.

More than a third of the 16-50s have failed so far! And the failure rate of the 50-135s is also clearly unacceptable.

In fact I would maintain more than a couple of failures throughout the lens range is unacceptable. These are expensive units that one would expect to last many, many years...all my screw focus lenses still work and some are getting quite ancient.

We really need this problem sorted out.

[Canada_Rockies]

Actual numbers over the entire run seem to indicate that the unacceptable DA* 16-50 lenses are somewhere between 2.5% and 5% of the total production. Still high for the price, but not as catastrophic as some make out.

[jthommo]

Actual numbers over the entire run seem to indicate that the unacceptable DA* 16-50 lenses are somewhere between 2.5% and 5% of the total production. Still high for the price, but not as catastrophic as some make out.

Interesting. Your source?

[PentaxPoke]

Actual numbers over the entire run seem to indicate that the unacceptable DA* 16-50 lenses are somewhere between 2.5% and 5% of the total production. Still high for the price, but not as catastrophic as some make out.

Albert,
I don't quite follow. How do you get those numbers? It looks like the SDM failure rate amongst Pentax enthusiasts (people who contribute to the forums) is remarkably high. I wonder how many people who don't follow the forums are limping along with a lens that Sometimes Doesn't Move.

[stevebrot]

Albert,
I don't quite follow. How do you get those numbers? It looks like the SDM failure rate amongst Pentax enthusiasts (people who contribute to the forums) is remarkably high. I wonder how many people who don't follow the forums are limping along with a lens that Sometimes Doesn't Move.

The SDM failure rates are "remarkably high" for those that choose to participate in the polls. Traditionally, people with no problems also have no comments. As a result, the incidence of failure may be as high as the poll indicates, but more likely is somewhat less.

So where do you go for good data? The gold standard for quality issues is the frequency of return for warranty service. Unfortunately, makers are not usually going to share that data unless it looks really good for marketing purposes. Anecdotal evidence (word of mouth reports) is that the numbers are close to the figures stated by Albert and are representative for the industry in general.

Now, if you look at my signature, you will notice a conspicuous absence of SDM lenses. This is mostly by accident, but is also partially due to a hesitancy to invest that kind of money in complicated moving parts that have the potential to wear out fairly quickly.

Steve

[PentaxPoke]

The SDM failure rates are "remarkably high" for those that choose to participate in the polls. Traditionally, people with no problems also have no comments. As a result, the incidence of failure may be as high as the poll indicates, but more likely is somewhat less.

So where do you go for good data? The gold standard for quality issues is the frequency of return for warranty service. Unfortunately, makers are not usually going to share that data unless it looks really good for marketing purposes. Anecdotal evidence (word of mouth reports) is that the numbers are close to the figures stated by Albert and are representative for the industry in general.

Now, if you look at my signature, you will notice a conspicuous absence of SDM lenses. This is mostly by accident, but is also partially due to a hesitancy to invest that kind of money in complicated moving parts that have the potential to wear out fairly quickly.

Steve

I agree with you steve. I also think that people who frequent the Pentax forums are more likely to actually know that there is something wrong with thier lens, as opposed to new DSLR users who may just think that is the way camera AF is supposed to work. They may not send it in for service until the SDM is actually dead as opposed to working intermittently.

Bottom line though is that I still maintain that this is a big problem. How many posts have you ever read about a Pentax DSLR body AF motor failing, or the failing of the focus mechanism on any non-SDM Pentax lens made in the last several decades.

I suspect where there is smoke, there is fire, and I see a LOT of smoke...

Those statistics DO NOT look good even if there's a bias! I've been pondering for months whether to buy a DA* zoom or not. I think this was the last straw for me.

Any direct link to the source? Or is it a verboten source?

EDIT: OK, found it with Google. A poll of yours, it seems.

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Last edited by emr; 09-16-2009 at 12:05 PM.

Over in the other place a poll of SDM lens failures makes unedifying reading; the results so far:

16-50: 17 failures from 49.

I quickly checked (and probably misinterpreted and miscalculated) and figured it's 23/59 by now.

[Alfisti]

The real concern is not so much that poll (I poll for a living so I won't start pointing out the flaws in the methodology) but the constant stream of evidence. you have thread after thread on both forums with SDM failures and you have almost every lens review of a DA* or DA SDM lens from Dpreview or Photozone, saying they had to send it back a few times to get a good one.

NOT GOOD.

[PentaxPoke]

The real concern is not so much that poll (I poll for a living so I won't start pointing out the flaws in the methodology) but the constant stream of evidence. you have thread after thread on both forums with SDM failures and you have almost every lens review of a DA* or DA SDM lens from Dpreview or Photozone, saying they had to send it back a few times to get a good one.

NOT GOOD.

And the reason that they keep having to send them back is not because of SDM failures, (since they MF for those image tests) but because of optical problems like decentering (same as my multiple DA* 16-50's) So they have two types of QC problems on DA* lenses.

People that have working versions of these lenses can talk all day about how much they love them, but that doesn't help the many of us that have had bad versions. Think about it: how many problems have people reported about focus mechanisms and decentering issues for the past decades on Pentax lenses that are not DA*? I suspect very few. I can't recall a single one that had a problem that wasn't a result of dropping it or fungus. Only the DA*s.

Oh yeah, and I have been shooting Pentax since '82.

[deadwolfbones]

Should mention that it's not only Pentax who are having problems with HSM/SDM/USM motors. Sigma also has a huge issue with some of their lenses.

[PentaxPoke]

Should mention that it's not only Pentax who are having problems with HSM/SDM/USM motors. Sigma also has a huge issue with some of their lenses.

Doesn't make me feel better. In fact makes me feel worse...for Pentax to be compared with Sigma. Pentax has a long history of quality glass. In fact that reputation still exists today with photographers using other brands, based on that long history. Sigma (rightly or wrongly) in the past has been thought of as budget glass and had QC problems.

[kenyee]

Should mention that it's not only Pentax who are having problems with HSM/SDM/USM motors. Sigma also has a huge issue with some of their lenses.

Pentax's SDM is also a different design. It's really a micromotor, not unlike the Tamron internal motor lenses for Nikon/Canon.
Sigma's HSM is a ring motor...the rollers in the initial copies apparently crapped out. They stepped up after recognizing the problem and increased their warranty period however...

[jthommo]

16-50: 19 failures from 55.

50-135: 13 failures from 73.

17-70: Two failures from ten.

200: One from 11.

300: One from 22.

60-250: all good from 13 so far.

55: Eight good copies.

Of course these polls are not as accurate as if a polling company had approached random Pentax SDM lens owners. But they do show a clear trend.

And no matter how many excuses people come up with why the SDM fails the reality is that there is a major design fault here. We paid big bikkies for these lenses and we want them to work - that's surely not too much to ask.

[Oggy]

I wonder if this is really representitive. I would guess that people who have had failures are more likely to reply to this type of post.