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08-23-2010, 01:39 AM   #16
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QuoteOriginally posted by blende8 Quote
The way Pentax introduced in-lens motors, was really bad.
These mini motors are just crap.
They are very slow and they fail often.
I have word from someone who knows this stuff, who disassembled his SDM lens and was shocked about the poor and cheap construction.
Only advantage is they are more silent.
Pentax is offering not even the minimum of support, namely the use of shaft AF in case the SDM is failing.
I wouldn't complain if they were using this in their budget lenses, but they are using it in their premium line!

Real robust ring motors please!
although I didn't have the pleasure of getting a closer look of the insides of an SDM lens, I however have this thought that the mechanism was brittle. if it's any help or consolation, it would be helpful if some pictures can be provided for customer awareness of what the product they are going to buy is made of. this is not a sabotage nor a smear job for Pentax, but rather an awakening for Pentax that people are got eyes on them and would be watching carefully. for such a weak construct, I believe they should exactly worth when they first came out of the market, at $500-600 dollar limit. having said that, at such a price tag, failure should not even be an option as well.

08-23-2010, 01:41 AM   #17
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QuoteOriginally posted by ogl Quote
The main problem of SDM construction is weak material of driving gear.
It could be broken even during guarantee period.


Yes. It's from some kind of polymer plastic, but I don't understand WHO prevents Pentax to change the supplier of components or change the material of details to more solid????
kinda reminds me of the 1st generation XBOX 360. strong graphics processor with substandard cooling system.
08-23-2010, 01:59 AM   #18
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QuoteOriginally posted by Pentaxor Quote
kinda reminds me of the 1st generation XBOX 360. strong graphics processor with substandard cooling system.
M$ were very coy on this for a long time to.
08-23-2010, 02:18 AM   #19
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QuoteOriginally posted by ogl Quote
The main problem of SDM construction is weak material of driving gear.
It could be broken even during guarantee period.


Yes. It's from some kind of polymer plastic, but I don't understand WHO prevents Pentax to change the supplier of components or change the material of details to more solid????
I've read somewhere that the motors have been changed so that the problem now should be solved. I don't know if that matches with user experience though. Are there still problems with newer SDM lenses?

08-23-2010, 02:34 AM   #20
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QuoteOriginally posted by Gimbal Quote
I've read somewhere that the motors have been changed so that the problem now should be solved. I don't know if that matches with user experience though. Are there still problems with newer SDM lenses?
The general 'internet opinion' seems to be that whilst you still do get SDM failures the only two lenses that suffered from apparently abnormal levels of this were the 16-50 and 50-135. The later lenses appear to have normal failure rates.

I add the caveat that no one can actually make any reliable statements along these lines because no one actually has the failure figures except Pentax (and even then they may not have global ones). This is why I used the term 'internet opinion'.
08-23-2010, 02:37 AM   #21
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QuoteOriginally posted by Gimbal Quote
I've read somewhere that the motors have been changed so that the problem now should be solved. I don't know if that matches with user experience though. Are there still problems with newer SDM lenses?
But it is not enough to have a HEARSAY that some motors were changed, I wan to know for sure! So, as Boris suggested, Pentax should admit the failures and make clear that new lenses are corrected as from some point.

If they do not wish to admit failures, at least they should make a clear change, say, announcing a new breed of SDM II, so that we could KNOW improvements have been made, and preferably also with a new ring type technology!
08-23-2010, 02:42 AM   #22
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QuoteOriginally posted by Caat Quote
The general 'internet opinion' seems to be that whilst you still do get SDM failures the only two lenses that suffered from apparently abnormal levels of this were the 16-50 and 50-135. The later lenses appear to have normal failure rates.

I add the caveat that no one can actually make any reliable statements along these lines because no one actually has the failure figures except Pentax (and even then they may not have global ones). This is why I used the term 'internet opinion'.
Well, have you ever heard about mechanical AF mechanism stuck in the lens? Have you ever read in the forum about failed AF motor in camera?

I haven't. However I have read tons of post about SDM failures on DA* lenses.

It seems that Pentax SDM fails because it simply wears out. So, it is self explanatory, that you don't hear about SDM failures of newer lenses. Wait some time and I bet that reports about SDM failures on DA* tele primes and DA 17-70mm will start to emerge.

Last edited by Edvinas; 08-23-2010 at 02:48 AM.
08-23-2010, 02:50 AM   #23
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QuoteOriginally posted by Edvinas Quote
I haven't. However I have read tons of post about SDM failures on DA* lenses. Thing is that Pentax SDM fails becaus it simply wears out. So, it is natural, that you don't hear about SDM failures of newer lenses. Wait some time and I bet that reports about SDM failures on DA* tele primes and DA 17-70mm will start to emerge.
Sure, but 16-50 and 50-135 had multiple SDM problems right from the start, which is not AFAIK the case of newer lenses. It's not like many people was moaning about 17-70 or 55/1.4 SDM failures. There are probably, but nothing comparable to those two other lenses.

That should also be taken into account although an SDM II with true ring type motors would be ideal.

08-23-2010, 02:56 AM   #24
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QuoteOriginally posted by thibs Quote
Sure, but 16-50 and 50-135 had multiple SDM problems right from the start, which is not AFAIK the case of newer lenses. It's not like many people was moaning about 17-70 or 55/1.4 SDM failures. There are probably, but nothing comparable to those two other lenses.

That should also be taken into account although an SDM II with true ring type motors would be ideal.
Indeed. Also I think the fact that the 16-50 also had lots of decentring issues as well points to generally bad quality control on that particular lens at the beginning of it's production which may have contributed to, or been related to, it's apparent SDM issues.

I would think that new lenses released in Septermber, if any are SDM, will either be branded SDM II or reference will be made to the system being improved - but improved in terms of speed (I don't expect Pentax to make any reference to SDM failing or anything).
08-23-2010, 05:25 AM   #25
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QuoteOriginally posted by ogl Quote
The main problem of SDM construction is weak material of driving gear.
I've disassembled a 16-50mm with defective SDM, and to me the mechanical parts did not seem inferior to other contemporary lenses. I came to the conclusion that either the motor itself had died or the electronic components controlling it.

Based on the fact that the focusing got gradually worse before complete failure, instead of just dying instantly, I would suspect it was the motor itself that was the problem.
08-23-2010, 05:36 AM   #26
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Thank you, but NO for SDM.

At least for micro-motor and dual-AF (screw-drive + SDM) type.

Only pure ring-type SDM-Only lenses if so, or reliable screw-dirve
08-24-2010, 02:03 AM   #27
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I am very happy with my DA 17-70 f/4 SDM. Smooth, near silent focusing. It is fast too.
Users are complaining about SDM being slow, but that is because screwdriven and SDM are equal in terms of speed - and they are equal because the limitation is in the camera - the AF processing in the camera - and not the lens.

Some believes that in-lens motors are faster than screwdriven, if they are not then something is wrong. In the 90's, the screwdriven AF that Pentax used was clearly faster than in-lens motors. The MZ-5 with FA 28-70 f/4 AL was a rabbit in terms of AF speed compared to similar priced Canon EOS 50E with 28-80 USM. The in-lens motor driven Canon was a turtle and Pentax was the rabbit. (according to tests made by swedish magazine FOTO).

It is a long myth, coming from Canon, that in-lens motors automatically should mean faster AF. It is not about the technology, but how it is implemented.

So the advantages with in-lens motors are not the speed, it is the smoother focusing with lower sound. Speed is largy dependant on the AF processing in the camera, not the technology in the lens.

Another factor is the focus throw of the lens.
The DA Star 55 f/1.4 is slow because it has a long focus throw. The DA 17-70 f/4 SDM is faster because it has a short focus throw.
08-24-2010, 04:15 AM   #28
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To me, I don't really care to have SDM added to older lenses, but I would like to have weather sealing on some of them. SDM is almost exactly the same speed as the screw driven motor. If adequate auto focus can be achieved with one, it should be able to be done with the other. The problems that I have seen have nothing to do with speed at which the lenses are driven, it is the fact that they tend to "miss" in poor light and cycle through the whole focus throw till they lock on.
08-24-2010, 04:27 AM   #29
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QuoteOriginally posted by RMabo Quote
Another factor is the focus throw of the lens.
The DA Star 55 f/1.4 is slow because it has a long focus throw.
This is no argument.
AF and MF mustn't be the same, see DA200.
08-24-2010, 04:41 AM   #30
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DA 21/3.2 ltd has quick shift focus (which is most useful), is small and its AF is screwdriver driven. If Pentax introduced FA limited lenses with quick shift focus, I think it would be really welcome idea.
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