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01-09-2010, 08:35 PM   #31
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All my AF lenses are screw drive and I like them!
Nanah nanah poo-poo!

Electric motors should, and have been in the past, had longevity.
I will avoid them as long as humanly possible.

01-09-2010, 09:28 PM   #32
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QuoteOriginally posted by Raybo Quote
All my AF lenses are screw drive and I like them!
Nanah nanah poo-poo!

Electric motors should, and have been in the past, had longevity.
I will avoid them as long as humanly possible.
Like a pervasive nightmare it will invade your life when you least expect it, and there's nothing you can do about it. Mwuhahahaha!
01-09-2010, 11:23 PM   #33
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QuoteOriginally posted by Ash Quote
Like a pervasive nightmare it will invade your life when you least expect it, and there's nothing you can do about it. Mwuhahahaha!
I'm fortunately observing from the sidelines here, not owning any SDM lenses or SDM-capable cameras. It's easy to get the impression that the DA* 16-50mm lenses are pretty unreliable beasts, possibly on the verge of failure. People have attempted to quantify this failure in different forums, counting separate failure claims. It doesn't look good for this lens and SDM technology.

So my question is, what is the value of this lens? The retail price is $744 US from B&H or Adorama. I would seriously consider an extended warranty, given the anecdotal evidence. That price is unlikely to change.

The really curious thing is the used price. I found ten Sold threads in the archives for US lenses advertised as working fine with no issues, all within the 6 months that this has been a hot issue, and the price is steady between $600 and $650. Three European lenses sold for between 510 and 580 euros, and two Australian lenses sold for $760Au and $800Au. Why isn't the price plummeting for lenses that are doomed to fail?

Another curiosity: the only broken lens for sale had fallen from a tripod. Remember, failed SDM lenses will still AF on the *ist series, K110D and non-Super K100D cameras. Because of that, they would have some value, probably more than the Tamron 17-50/2.8. I suppose this means that lenses are being repaired even out of warranty.

Either situation implies more "consumer confidence" about this lens than I would feel after reading many discussions like this.
01-09-2010, 11:31 PM   #34
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I hope some Pentax employees here are reading or paying attention to these SDM failure threads right now. this would definitely affect Pentax as a whole.

01-09-2010, 11:41 PM   #35
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I have seen the insides of a DA* 16-50mm and I have to say the SDM motor is tiny, about the size of a 10 cent coin/penny. Given the initial hype surrounding the promise of silent focusing (given that so many complain how noisy screw drive is), a lot of people went out to buy the 16-50mm as it has a useful range of focal lengths and there was compatibility with non-SDM capable older camera bodies. I personally think Pentax rushed to deliver the product and probably could not do extensive enough field testing to ascertain the reliability of the SDM motors. If I remember correctly, Pentax Japan (pre-Hoya) had to issue a press release to apologize for not being able to meet the pent up demand for the lens. Now as to why the lenses are failing now (typically close to the 1 year warranty period), my guess is most users most don't use it often enough for the issue to show up early enough. Obviously Pentax might incorporate more robust SDM in the assembly line in later batches but the negative reputation has already been done. I'd suggest the Pentax design engineers go back to the drawing board and redesign using ring type ultrasonic motors if not SDM will forever refer to Self Destruct Mode.
01-10-2010, 12:18 AM   #36
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I've been with Pentax since 1981......I have the 16-50, 50-135 and 300, and luckily, so far so good. I have to admit, this is giving Pentax not only a black eye, but because they stay in the ring without doing anything, they are getting bloodied and brused. While I love mine, if there is an issue, they need to stop production and replace them with a corrected SDM II, or enable the screw. The longer they ship a faulty product, the more Pentax loyailsts they send packing.

Pentax won't send someone on the site to chat about this...all they can do is announce a replacement product.....which should be fast tracked....hello?....Pentax....are you listening?
01-10-2010, 12:21 AM   #37
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Peter, it is sad indeed. But given that cameras and lenses are just tools, I think that it would make sense for you to seriously consider buying into another system. After all, you have all the numbers and can do the math properly. If it turns out that Canon or Nikon or Sony hold more financial sense to you, then by all means - you ought to take your time and consider. People like me who are amateurs and hobbyist often can work around these issues as they don't have photographic obligations, so to say. Most likely you will produce brilliant pictures with any camera and lens after you passed the learning curve, which is very likely to be quite short.

Sad, but true - sometimes you have to let go.
01-10-2010, 01:46 AM   #38
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Yes, it's a little different for an enthusiast compared with someone relying on their equipment for their daily bread. The 16-50 has done remarkably well for me - and I've turned to it for each of my big jobs - but I don't do such jobs everyday nor do I rely on that income for survival.

I've admitted each time this issue comes up though that SDM reliability is dubious and its robustness is questionable, so for someone like Peter, Canon/Nikon offer more attractive packages that are at least more reliable if not more robust AF than Pentax SDM. Cost is a significant issue, though...

01-10-2010, 03:15 AM   #39
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Peter, I do understand your frustration.
From what I understand from how focusing works, it is the camera that guesses the position of the in-focus based on electronics from the lens telling the camera how to compute the parameters.
So, there are two possibilities.
When your lens was built, the wrong parameters were encoded with the chip. Or
Your current camera has problems with the specific set of parameters encoded.

I think the latter may be the culprit. On the K10D, all my lenses (18-55, FA35, 70-300 Tamron) focused spot on, but the 16-50 BF'ed majorly.
On the K-x, all lenses focus correctly. (yes, even wide open for the FA35 and the 16-50).

I think specifically with the 16-50, the parameters encoded are often difficult for cameras to cope with. In your case, it sounds like the focus is spot-on, but the camera wrongly predicts where to go in little contrast, which could mean that the parameters are just slightly off. And while it may be completely unsatisfactory, sending the camera in with the lens may help them to correct your issue.

It is sad that the 16-50 has issues for a somewhat large group, because it is otherwise such a good lens for most of us.
01-10-2010, 07:22 AM   #40
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Perhaps they should just drop the dual SD/SDM system and go with either or. The combined system must add a lot of unnecessary complexity that evidently screws up (no pun intended ). For example, It seems like the DA* 55 doesn't have any real problems with it's SDM-only design.
01-10-2010, 07:26 AM   #41
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QuoteOriginally posted by Peter Zack Quote
Maybe it's not the SD but that it's a zoom. We hardly hear anything about the 200mm or 300mm. Mostly this lens and the 50-135mm to a lesser extent.
And now it's 17-70 which does not support SD.
01-10-2010, 12:08 PM   #42
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QuoteOriginally posted by joakimfors Quote
Perhaps they should just drop the dual SD/SDM system and go with either or. The combined system must add a lot of unnecessary complexity that evidently screws up (no pun intended ). For example, It seems like the DA* 55 doesn't have any real problems with it's SDM-only design.
Maybe not yet, but it is slower than the original FA 50 f/1.4! That is not an encouraging direction to be going.
01-10-2010, 12:59 PM   #43
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I actually don't mind that there's a dual SD and SDM system. I can't see Pentax ever doing away with SD given the success with all the FA and DA limiteds, but I also hope that Pentax don't abandon SDM development - I'm sure it *can* be made more reliable, fast and robust than it is now and at least comparable to Nikon & Canon's ultrasonic AF systems. So what if it'll cost more? That's why we're paying extra for the technology - it's worth it. Add WR and superior build quality to the mix and the DA*s could conceivably be worth a little more than they are now (with those SDM improvements mentioned earlier).
01-10-2010, 02:57 PM   #44
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Peter,

I'm very sorry to see you this frustrated about the lens and the response by Pentax to your troubles.

I have some questions:
  1. What is the exact problem you have with the lens?
    1. Is the SDM too slower and/or slower than SD?
    2. Does low-light focusing work with SD but not with SDM?
    3. Are you worried that your lens is developing an SDM failure?
  2. What is your experience with the K-7 and your 16-50?

If your problem concerns focusing in low light, independently of SDM/SD and the camera body, then I'm sceptical Pentax can easily address this. You and others say the lens is great optically and I guess its focussing behaviour is part and parcel of that.

If I were you I would seriously test the K-7 and see how that helps the low light focusing with the 16-50. After all, the AF system is in the camera and while a lens can make it easier or harder for a body to achieve focus, a better body (i.e., K-7 instead of K20D) might just solve your problem.

Regarding SDM reliability: Somewhere I've read someone stating that the issue is with a connection within the lens which should have been designed more robustly, i.e. no problem with the technology as such. If that really is the case it shouldn't be that hard to address by Pentax and one can understand that they will probably do it behind the scenes and not publicly announce a "reliable SDM II".

Regarding SDM speed: There is this quandary between quick AF and precise AF / acceptable MF. Other manufacturers may have addressed this already but currently Pentax SDM seems to sacrifice speed in order to get the other advantages. My guess is it will take them a while to get a faster version of SDM since fast AF cannot be their priority given their position relative to Canikon.

QuoteOriginally posted by Peter Zack Quote
The Tamron 17-50mm is having issues as well.
What issues? FF/BF?

I have no idea what the proportion of a potential 16-50 QC problem is and/or how unreliable SDM really is. I guess only Pentax and the repair centres have the numbers. It might be true that, when seeing the big picture, their is no real problem. But for a user who has a 100% trouble with the lens, it is no consolation that on a global scale the percentage of problems is acceptably low. I wished the responses by Pentax where more accommodating and their representation on the forum here is a very sad affair. Quite hard to believe actually. They must be doing well without extending their attention to (one of?) the largest Pentax user group.

I hope you get your trouble sorted soon.

Last edited by Class A; 01-10-2010 at 03:07 PM.
01-10-2010, 03:06 PM   #45
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QuoteOriginally posted by Class A Quote
What issues? FF/BF?
*In reality* focusing is affected by spherical and chromatic aberration BUT if you have a problem with a lens front focusing or back focusing, it's most likely a problem with the body or because the AF system is not calibrated for tungsten light. Blaming a particular copy of a lens on FF/BF makes no sense to me.

Here's a potential problem (loose screws):
http://www.youtube.com/watch?v=IiOj-7MAO_w
which fortunately can be fixed by yourself, unlike an SDM problem.
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