[ben_leg]

I have been doing a lot of soul searching lately...

By looking at the reviews (comparing new lenses), it seem that the DA* (16-50 and 50-135) are a relatively good value, especially considering that they are WR.

But looking at the different thread around here, it seem that the DA* have a reliability issue.

So I’m wondering if all those threads are simply because a normal amount of people have issue with their lens and they complain about it over here (after all there is no better place to do it).... or there is really a reliability issue with that series???

Has an hobbyist, the only way that I could justify such an upgrade is if I could use my equipment well pass it’s warranty coverage.

[twitch]

No one knows for sure whether the failure rate of SDM lenses is above industry average for lenses with motors in them, that's becuase Pentax has never published figures. It seems given the amount of noise generated on this forum, and th enumber of people suffering mutliple failures, that the failure rate is relatively high still.

My advice, by all means buy one but it might be wise to buy an extended warranty with it (5 years if you can afford it).

[luke0622]

I had previously owned every single DA* lenses, I had never had any issues with them. I even had my DA* 16-50mm/2.8 and K-7 in the relatively heavy rain for 3 hours without and covers on, and there was not a single issue. Well, I would not recommend you to do so, but, just trying to prove a point here. There seemed to be more problems when the first came out, I don't think you really need to worry about it now, don't let the web negativities stop you taking photos with those beautiful DA* glasses.

[Ash]

The issue is very real to those who have experienced it, so you'll have to expect this to be reflected on fora such as this one. OTOH, there is no denying the value of these lenses is in their optical quality and solid build. The WR feature is reliable and microcontrast excellent. AF function is no faster than that of the screwdriven lenses, but is silent. This is the most concerning part of the lens as most of the faults seem to be centred around the SDM. I certainly enjoyed shooting with my DA* but would recommend potential buyers to take out extended warranty to cover for any SDM failure.

[philbaum]

No one knows for sure whether the failure rate of SDM lenses is above industry average for lenses with motors in them, that's becuase Pentax has never published figures. It seems given the amount of noise generated on this forum, and th enumber of people suffering mutliple failures, that the failure rate is relatively high still.

My advice, by all means buy one but it might be wise to buy an extended warranty with it (5 years if you can afford it).

I agree with twitch on this one and also Ash, for that matter,

I've never been a "first responder" when it came to new equipment, and seem to have avoided initial teething problems with a variety of bodies and lenses.

The only lens of the two you mentioned that i have is the 50-135. The character and rendering of this lens never ceases to delight me. I took it out in a heavy snowstorm last Thursday, and 2 of the pictures i posted on the local photoclub's website got a lot of raves. Been about 2 years since i bought and its working fine. If it failed tomorrow, i'd get it repaired. I've got other good lenses, but this one is special, very special.

A picture from this lens won my club's "photo of the year" in 2010. Its sold 3 times in 2010. This year it got accepted in a juried Washington State wide contest run by local gallery in which one of every 7 art objects got rejected. When i went to pick it up on Feb 26th at the end of the exhibition, they refused to return it, sayiing its been sold (for the 4th time). you'll have to pry the lens out of my "cold dead hands" :-)

[Class A]

But looking at the different thread around here, it seem that the DA* have a reliability issue.

The sad truth is, they do.

When the SDM issues started there was a lot of hysteria and I was one of the few stating that there was too little evidence to justify a petition, etc. Since then the SDM failure reports haven't stopped. Surprisingly many have their lens fail not once, but twice or even three times.

Lenses can fail, yes, but in particular these multiple failures with single individuals and the frequency with which I read about SDM failures tells me that there is a fundamental problem and that one does not have to be particularly unlucky to experience an SDM failure.

The primes seem to be more robust but in particular the 50-135 and the 16-50 seem to be affected a lot. It would have been more than appropriate for Pentax to increase the measly one year warranty to at least three years for a so-called "*" lens. In comparison, in some countries, Sigma lenses have six years warranty. Maybe it has to do with the fact that HSM failures seem to be very rare? Can you find a analogue HSM thread where users are happy like children at Christmas just because someone found a way to repair a particular SDM failure?

I agree, optically the 50-135 is a gem, but if I were you, I wouldn't buy it without an additional warranty.

BTW, the AF of the 50-135 is slow. Period. Let's call a spade a spade. Screw-drive lenses experienced a boost through the stronger K-7/K-5 AF motors but SDM lenses will always have the same (typically slow) speed. In some cases, this is not a problem, e.g., the DA *55 is meant to be a portrait lens and hence precision is more important than speed, but you won't be able to capture fast action with the 50-135 to the same degree as with a quicker screw-driven or HSM lens.

[Rondec]

These threads are tough because no one knows anything about the rates of failure of these lenses. All we can say is that they fail at a significantly higher rate than screw driven lenses do, but since screw driven lenses seldom have auto focus failure, that doesn't tell me much at all.

As to speed, it has been tested and it is exactly the same as the screw drive. The 50-135 is a slow focusing lens because it has such a long focus throw, but the 50-135 focus quite slowly when used with the pre-SDM firmware on K10's as well. The 16-50 and 17-70 both focus faster than the 50-135 because their focus throws are much smaller.

[philbaum]

These threads are tough because no one knows anything about the rates of failure of these lenses. All we can say is that they fail at a significantly higher rate than screw driven lenses do, but since screw driven lenses seldom have auto focus failure, that doesn't tell me much at all.

As to speed, it has been tested and it is exactly the same as the screw drive. The 50-135 is a slow focusing lens because it has such a long focus throw, but the 50-135 focus quite slowly when used with the pre-SDM firmware on K10's as well. The 16-50 and 17-70 both focus faster than the 50-135 because their focus throws are much smaller.

I suspect that many do a lot more AF than they need to. For live theatre stage work, i learned to disable the half shutter AF, and switched to AF button focus. By using a smaller aperture with more DOF that cover a larger area of the stage, i would focus only every 7 shots or so, rather than put AF in series with EVERY shot. makes a big difference in one's reaction time. With improved ISO of kx, kr and k5, use of smaller apertures can be done without lowering IQ due to noise.

Also, a slow focusing ZOOM lens can be faster than a fast focusing PRIME lens if it keeps one from having to change lenses out, the slowest operation of all.

Yes, there are situations where the fast focusing is important, and many others where it isn't important. Just saying it comes down to the type of applications that you need the equipment for.

I may be wrong, but i think the incidence of 50-135 failure reports is less than it was. at least i hope thats the case.

[RonHendriks1966]

That is a difficult one. I had one dead 16-50, but that was dead on arrival, not SDM but internal things loose, so a replacement and that was fine, but sold it because it wasn't my thing. I have a DA*55mm and it's a great lens and no trouble in 2 years. I have a DA*50-135, two years old now and works fine.

I know some people with trouble and a lot more with no trouble. The suggestion of extended warranty is a good one.

[Class A]

These threads are tough because no one knows anything about the rates of failure of these lenses.

It's not just the dedicated threads where you would expect a lot of affected users to concentrate and provide a skewed view on the issue.

It's the repeated "in passing" mentioning of users reporting about SDM failures when talking about different subjects (e.g., lens recommendations). It basically has become an acknowledged problem. I cannot recall anyone responding with "What? This shouldn't happen with a lens of this calibre!" lately. Instead, no one really comments on an SDM failure mentioning anymore.

And just observe how many recommend to take up an extended warranty. I don't think such a recommendation should be necessary for a top-of-the-line lens. It should be known to be very reliable and/or come with a decent warranty period.

I'd have no trouble buying any screw-driven AF lens used. But an SDM lens where the warranty has expired? Hell no, unless I'd get it for the price of an MF lens. I haven't analysed this but the SDM failure reports -- in this case independently of whether they are blown out of proportion or not -- ought to have an impact on resale values. Or do they?

[Rondec]

It's not just the dedicated threads where you would expect a lot of affected users to concentrate and provide a skewed view on the issue.

It's the repeated "in passing" mentioning of users reporting about SDM failures when talking about different subjects (e.g., lens recommendations). It basically has become an acknowledged problem. I cannot recall anyone responding with "What? This shouldn't happen with a lens of this calibre!" lately. Instead, no one really comments on an SDM failure mentioning anymore.

And just observe how many recommend to take up an extended warranty. I don't think such a recommendation should be necessary for a top-of-the-line lens. It should be known to be very reliable and/or come with a decent warranty period.

I'd have no trouble buying any screw-driven AF lens used. But an SDM lens where the warranty has expired? Hell no, unless I'd get it for the price of an MF lens. I haven't analysed this but the SDM failure reports -- in this case independently of whether they are blown out of proportion or not -- ought to have an impact on resale values. Or do they?

I am not certain that I understand your point. I own three SDM lenses. I have had one of them fixed under warranty, nearly two years ago that is functioning fine at this point. The others have had no issues. Overall, I would say that my experience has been positive. However, I mention SDM as a possible issue every time someone mentions these lenses because I don't want them saying that they have not been warned.

I think the optics of these lenses do warrant their purchase and I don't think that an extended warranty (costing perhaps fifteen dollars to add five or six years) is either a huge cost or, an unreasonable idea. Even if these lenses were sold with a three year warranty, it wouldn't be a bad idea to double your length of coverage.

I wish that Pentax would at least quantify the problem, but even then , it would be impossible to say anything about the statistics without data from the other camera companies to compare it to.

[JHD]

These threads are tough because no one knows anything about the rates of failure of these lenses.

Actually we know SDM lens failure rates are very high, so high they are regularly reported unlike other Pentax and third party lenses... And even after they are 'repaired' so speak, they fail again... and again. So as long as people buy DA* lenses, we can be sure there will be more reports of SDM failure. I for one would not buy a product with known and on going issues. There’s no substitute for reliability.

[dgaies]

Actually we know SDM lens failure rates are very high, so high they are regularly reported unlike other Pentax and third party lenses...

While I have no doubt they fail at a rate much higher than other Pentax and third party lenses, that still doesn't tell us anything about the actual failure rate. Let's say that regular screw driven Pentax lenses have AF failures at a rate of about 1 in 10,000 (0.01%) and SDM lenses have a failure rate of 500 in 10000 (5%). That would mean that SDM lenses fail at a rate 500x what a screw driven lens fails at, and would be consistent with the fact that they are reported with such a higher frequency. But a lot of people would like to know what that actual failure rate is such that we'd have a better idea what the likelihood that a given SDM lens will fail during a certain period of time. Just knowing it's a lot higher than a screw driven lens doesn't give people the information that would help them make informed decisions regarding SDM lens purchases.

[twitch]

Well there is a hint that SDM failures are very high.

Lens Rentals which publish faliure rates for their lenses have dropped some lenses which are alos avialable in PK mount as they found them failing too often compared to the Canon & Nikon ones.

There are three reasons a lens is not on the [failure rate] list:
<snip>
The lens has proven so unreliable that we’ve stopped carrying it. The following three lenses have been discontinued for this reason:
•Sigma 150-500 OS
•Sigma 120-400 OS
•Tamron 70-200 f/2.8

Also the Bigma makes it in at #9 highest failure rate on the list. No mention of the 50-150, not sure if they carry it or not.

On anecdotal evidence here, those lenses that Lens Rentals deem too unreliable certainly seem a lot more reliable than SDM lenses in PK mount.

[JHD]

Well there is a hint that SDM failures are very high.

Lens Rentals which publish faliure rates for their lenses have dropped some lenses which are alos avialable in PK mount as they found them failing too often...

Do they carry DA* lenses?