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06-27-2011, 07:28 AM   #1
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SDM Failures - Pentax vs Canon, Nikon

There has been a lot of discussion about SDM motor failures with Pentax lenses of late. As I own the DA* 16~50/2.8 this has been a concern to me as this particular lens seems to hold the poll position for SDM failures. I’m pleased to report no problems in the two years I have owned this optic. May the force continue to be with me.

In any case my question to forum members is this: Are Pentax SDM motors any more or less prone to failure than other makes such as Canon or Nikon? From reading various threads in this forum one would get the impression there are only two kinds of Pentax SDM motors – those that have failed and those that are about to. Personally, based on my experience with the DA* 16~50/2.8, I don’t believe this to be true. I don’t know if there is any empirical data out there but I’d be interested in finding out.


Last edited by 8540tomg; 06-27-2011 at 07:49 AM.
06-27-2011, 08:21 AM   #2
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It is generally regarded that the DA* primes with SDM (55mm, 200mm, 300mm) are not prone to SDM failure like the DA* zooms. I too own the DA* 16-50mm and haven't had any SDM failures yet. So, I don't think those two categories are true...

EDIT: this is a heated topic so I'm sure you'll see some varying opinions.
06-27-2011, 08:47 AM   #3
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QuoteOriginally posted by Ubuntu_user Quote
It is generally regarded that the DA* primes with SDM (55mm, 200mm, 300mm) are not prone to SDM failure like the DA* zooms. I too own the DA* 16-50mm and haven't had any SDM failures yet. So, I don't think those two categories are true...

EDIT: this is a heated topic so I'm sure you'll see some varying opinions.
Good point Ubuntu,

The Pentax SDM primes do appear to be more reliable than the zooms. Let me rephrase the question. I was actually curious if other manuafactuers AF motors are any more or less prone to failure than those supplied by Pentax. I suspect they share similar failure rates but some empirical data, if available, would be instructive.

Tom G
06-27-2011, 09:34 AM   #4
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QuoteOriginally posted by 8540tomg Quote
The Pentax SDM primes do appear to be more reliable than the zooms. Let me rephrase the question. I was actually curious if other manuafactuers AF motors are any more or less prone to failure than those supplied by Pentax. I suspect they share similar failure rates but some empirical data, if available, would be instructive.
I remember a post a while back from someone who either works for or knows the owner of a lens rental shop. This is the best I can remember, but I admit that I could be wrong.

All lenses, Nikon, Canon, Pentax, etc., has statistically similar failure rates, but the rate itself was rather high (15 % or something).

I think the problem is more with warranty. Pentax - 2, Nikon - 5. Canon's is worse, actually, but you typically see people here switching to Nikon, not to Canon (and vica versa, actually).

If the SDM lenses had a 5 year warranty, I think people would complain a lot less, een with the same failure rate.

06-27-2011, 10:01 AM   #5
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I think a lot depends on what you compare it to. Nikon and Canon have upper end lenses that have ring motors and are faster and probably more dependable. I think if you were to look at "silent wave" motors or their equivalent, you would find that they aren't a whole lot better than SDM if at all.
06-27-2011, 10:51 AM   #6
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QuoteOriginally posted by paperbag846 Quote
I remember a post a while back from someone who either works for or knows the owner of a lens rental shop. This is the best I can remember, but I admit that I could be wrong.

All lenses, Nikon, Canon, Pentax, etc., has statistically similar failure rates, but the rate itself was rather high (15 % or something).

I think the problem is more with warranty. Pentax - 2, Nikon - 5. Canon's is worse, actually, but you typically see people here switching to Nikon, not to Canon (and vica versa, actually).

If the SDM lenses had a 5 year warranty, I think people would complain a lot less, een with the same failure rate.
This is true. Plus I think Pentaxians are prone to making a "big deal" over manufacture issues.*


*Disclaimer: this statement is not aimed at anyone in particular, nor does it intend to negate QC standards.
06-27-2011, 10:51 AM   #7
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QuoteOriginally posted by Rondec Quote
I think a lot depends on what you compare it to. Nikon and Canon have upper end lenses that have ring motors and are faster and probably more dependable. I think if you were to look at "silent wave" motors or their equivalent, you would find that they aren't a whole lot better than SDM if at all.
This is true as well.
06-27-2011, 12:26 PM   #8
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QuoteOriginally posted by Ubuntu_user Quote
This is true. Plus I think Pentaxians are prone to making a "big deal" over manufacture issues.*
Well, maybe. I think we are also spoiled. A lot of us own at least one older lens (from the 70's, or even 60's). They just don't make them like that any more (even the limiteds... although they come VERY close). Screwdrive lenses are also pretty resilient (although noisy). You can confidently buy an old manual focus gem from the 70s and know that it will last you pretty much forever. When the new-fangled autofocus on your expensive zoom craps out, and you've never had problems with your screwdrive limiteds or manual focus primes from the golden age, it's easy to understand why people claim standards have slipped so much.

Way fewer Nikon users delve back into the lens catalogue because A) you need an expensive body to make full use of them, and B) Nikon has a lot to offer in the budget prime range, new. That stuff is well marketed and most newer users buy a bunch from the shop before they really realize they can look through craigslist. Canon users are even less likely to own an old lens (need for adaptor and all).

06-27-2011, 02:16 PM   #9
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QuoteOriginally posted by paperbag846 Quote
Well, maybe. I think we are also spoiled. A lot of us own at least one older lens (from the 70's, or even 60's). They just don't make them like that any more (even the limiteds... although they come VERY close). Screwdrive lenses are also pretty resilient (although noisy). You can confidently buy an old manual focus gem from the 70s and know that it will last you pretty much forever. When the new-fangled autofocus on your expensive zoom craps out, and you've never had problems with your screwdrive limiteds or manual focus primes from the golden age, it's easy to understand why people claim standards have slipped so much.

Way fewer Nikon users delve back into the lens catalogue because A) you need an expensive body to make full use of them, and B) Nikon has a lot to offer in the budget prime range, new. That stuff is well marketed and most newer users buy a bunch from the shop before they really realize they can look through craigslist. Canon users are even less likely to own an old lens (need for adaptor and all).
Ha, I've never actually thought of it like that before... But I think you're right. It makes perfect sense!
06-27-2011, 03:29 PM   #10
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Yes, Pentax SDM lenses are more prone to failure than Nikon and Canon, and there is some evidence for it. Lens Rentals explain in their most recent lens repair report how they dropped a few lenses from their catalogue because they were far too unreliable compared to their other lenses (mostly Canon & Nikon). The lenses dropped are also available in Pentax mount so we can make some comparison. The lenses were:
■Sigma 150-500 OS
■Sigma 120-400 OS
■Tamron 70-200 f/2.8

Pentax SDM zooms are far less reliable than these lenses, so if those lenses are the benchmark for unacceptable reliability, then there is good reason to believe Pentax SDM is far less reliable than Canon & Nikon.
06-27-2011, 04:06 PM   #11
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QuoteOriginally posted by twitch Quote
Pentax SDM zooms are far less reliable than these lenses
Without hard, scientifically compiled evidence, I don't think we can rationally make such an inference. Most people just don't have the same expectations as to quality when it comes to Sigma and Tamron lenses; and so there's the very real possibility that people may be less prone to complain about issues with those lenses, which gives the illusion that the Pentax lenses have more problems.

Also keep in mind that the problems Len Rentals reports with lenses go well beyond focus motors. There appear to be a lot of zoom sticking issues, for instance. It's possible that Pentax SDM zooms are prone to autofocus failure while Nikon and Canon zooms are prone to sticking. Of course, without any hard data, it's impossible to know one way or the other.
06-27-2011, 04:27 PM   #12
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Am I 100% sure about it? No I'm not, I don't live in such a world, the best I can do is make decisions or draw conclusions on the balance of probabilities. So what's more likely? Well my "best guess" is that Pentax SDM lenses are much less reliable than Canon & Nikon AF motor lenses and there is some evidence for that as I pointed out above. I'm willing to change my view if the data available to me changes, but until then that's my view.

I don't like the position of giving SDM the benefit of the doubt until here is categorical scientific evidience to the contrary, that kind of decision making is good for criminal trials, but not for drawing conclusions about the world.
06-27-2011, 04:44 PM   #13
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QuoteOriginally posted by twitch Quote
I don't like the position of giving SDM the benefit of the doubt until here is categorical scientific evidience to the contrary, that kind of decision making is good for criminal trials, but not for drawing conclusions about the world.
I agree with this, and I won't be buying any SDM lenses until I see some improvement (i.e., the DC motor in the 18-135) applied to the DA* line.

I'm merely suspicious, but I don't have tonnes of money lying around, so I want my lens to be an investment, not a disposable tool.
06-27-2011, 04:50 PM   #14
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QuoteOriginally posted by paperbag846 Quote
Well, maybe. I think we are also spoiled. A lot of us own at least one older lens (from the 70's, or even 60's). They just don't make them like that any more (even the limiteds... although they come VERY close). Screwdrive lenses are also pretty resilient (although noisy). You can confidently buy an old manual focus gem from the 70s and know that it will last you pretty much forever. When the new-fangled autofocus on your expensive zoom craps out, and you've never had problems with your screwdrive limiteds or manual focus primes from the golden age, it's easy to understand why people claim standards have slipped so much.

Way fewer Nikon users delve back into the lens catalogue because A) you need an expensive body to make full use of them, and B) Nikon has a lot to offer in the budget prime range, new. That stuff is well marketed and most newer users buy a bunch from the shop before they really realize they can look through craigslist. Canon users are even less likely to own an old lens (need for adaptor and all).
This is an angle I hadn't approached the problem from before; good thinking. As you said earlier, I do think the bulk of why SDM failure bothers Pentax users so much is the extremely brief warranty on Pentax products (and the long turnover in getting repairs). But the 'simply not knowing what it used to be like' factor is something I hadn't even considered for the Nikon/Canon camp and may very well be a valid component of the psychological response to equipment failure rates that may not differ much between brands at all.
06-27-2011, 05:06 PM   #15
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I've wondered why we don't hear of failures in the Tokina versions of the 16-50mm or the 50-135mm. I'd bet the motor was the same, but with a different set-up for the focus clutch, or lack of. The new Tokina motor in the 16-28mm f2.8 is also called a DC motor like the new 18-135mm. I got one in Canon mount and will see how it goes, it does have a 3 year warranty so I'm not worried.
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