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12-29-2009, 01:54 PM   #1
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Fed up with SDM failure? Then, skip this thread!

My 50-135mm DA "*S*T*A*R*" lens arrived about a week ago.
It traveled to and from an official Pentax repair center for a repair of its failed SDM.
The failure occurred "fully" only after the end of the warranty period; so, it was a paid repair.
The whole process took about two months; no big deal as I was not using this lens frequently. I had never used it routinely, anyway...
The SDM focusing was sluggish when I had tried it first after the repair. But, it was operating... So, it was "fixed"...

Today, while trying to answer the request of a forum user (about its focusing speed; see: https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/83743-superson...failure-5.html) I had it mounted to my K20D. Guess what! It was taking a second or two for the lens to show the first signs of movement! And, it was focusing after this loong lag period. During this period, nothing was happening (no sound as well) and I was just thinking that it had failed and dead again... (Remembering the fact that the whole failure story started exactly like this; late to start, sometimes focusing, infrequently focusing, not focusing at all).

Here are my questions to those who do not believe that there is an "issue" with the SDM in certain Pentax lenses (see the statistics in the above thread to see what is hinted at) and to potential Pentax people who might be visiting this forum in their spare time:
- What is the estimated and acceptable failure rate of a top-of-the-line zoom lens?
- How many of the failures are expected/estimated to occur within the warranty period? (User errors are excluded).
- What is the rationale in forbidding the use of the screw driven AF system in this particular lens? (Charging more for repairs?)
- How much "lag" is considered within acceptable limits for an SDM motor (like the one used in my lens) to start operating after the push of the AF button?
- How many times a repaired SDM zoom lens is expected to "auto focus" before failing similarly again? Ten? Twenty?
- For how many times should the owner of a failed DA* lens send it for re-repair? Is there a limit? Or does it just depend on how stupid he/she is?

For those who may think that I may be from some other camp, a troll or the like; the documents of purchase and repair of my lens is available for review for those who are really interested in those.

12-29-2009, 02:06 PM   #2
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I'm really sorry about your bad luck
12-29-2009, 02:06 PM   #3
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People have been warned. SDM is junk. Just that when some people wanted to believe in something so badly, they won't listen to logic. Buy Pentax if you can live with slot AF, but buy Canon if you want USM. SDM is for those who believed in faith.
12-29-2009, 02:08 PM   #4
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QuoteOriginally posted by bc_the_path Quote
The SDM focusing was sluggish when I had tried it first after the repair. But, it was operating... So, it was "fixed"...

Today, while trying to answer the request of a forum user (about its focusing speed; see: https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/83743-superson...failure-5.html) I had it mounted to my K20D. Guess what! It was taking a second or two for the lens to show the first signs of movement! And, it was focusing after this loong lag period. During this period, nothing was happening (no sound as well) and I was just thinking that it had failed and dead again... (Remembering the fact that the whole failure story started exactly like this; late to start, sometimes focusing, infrequently focusing, not focusing at all).
This is exactly what my first one did after "repair" and then the second did it as well. After that, Pentax sent me a new one, and then I promptly sold it. The only difference is that sometimes mine wouldn't work until I manually moved the focus ring back and forth to "wake it up." Then it would sluggishly start working routinely (Until I stored it for more than a day or so.) I am through with SDM roullette.

When Pentax makes a real ring-SDM focus motor, I'll consider buying another Pentax lens. Canon has been doing it for almost 20 years (1988). What is taking Pentax so long?

Bulent, get ready for the posts saying:

a) Did you try cleaning the contacts?
b) Are your batteries charged?
c) You must be doing something wrong.
d) Can you deactivate the SDM?
e) "I have the DA* ??? and no problems yet. There isn't a problem with SDM. Its just people on forums like to complain."


I feel your pain... IMHO, you might consider investigating a refund if at all possible. You could consider selling it as well, if the repair is under warranty with Pentax. You need to do something to get your money (or at least part of it) out, or you basically just bought yourself an expensive MF lens.


Last edited by PentaxPoke; 12-29-2009 at 06:05 PM.
12-29-2009, 02:18 PM   #5
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This thread shows ~20% SDM failure for 50-135....Kind of bad QC...
12-29-2009, 03:21 PM   #6
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I know using the screw-drive is "forbidden" on those lenses that have both SDM and screw-drive focusing when used on cameras that support SDM (ie DA* 50-135mm on K7)

But is it somehow possible to fool the camera into using the screw-drive anyways? Perhaps by "hiding" one or more of the contacts? Or would that mess up how the camera treats the lens?

I wish we could somehow reverse-engineer the firmware and add our own option to the custom menu for enabling screw-drive focusing on SDM lenses that also have the screw-drive shaft.
12-29-2009, 03:39 PM   #7
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QuoteOriginally posted by GoremanX Quote
But is it somehow possible to fool the camera into using the screw-drive anyways? Perhaps by "hiding" one or more of the contacts?
These have been tried by many different people to no avail.

Up to now, when the motor in an SDM lens fails, it fails.

The only way to use the screw-drive mechanism of an SDM lens is with a camera body that does not support SDM lenses (e.g. K10D with firmware older than 1.3).
12-29-2009, 03:40 PM   #8
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I can also understand the frustration shown by all affected by SDM failures.
Nevertheless, it's not worthwhile damning SDM technology altogether.
There are still many satisfied SDM lens users out there and the technology works flawlessly and reliably.
Again, another plug for Pentax to get its act together with making SDM better, and restoring consumer confidence in the technology.

12-29-2009, 03:45 PM   #9
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QuoteOriginally posted by Ash Quote
I can also understand the frustration shown by all affected by SDM failures.
Nevertheless, it's not worthwhile damning SDM technology altogether.
There are still many satisfied SDM lens users out there and the technology works flawlessly and reliably.
Again, another plug for Pentax to get its act together with making SDM better, and restoring consumer confidence in the technology.
That's an oxymoron of a post Ash. How can it work flawlessly and reliably when there has been a lot of failures?
12-29-2009, 03:54 PM   #10
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QuoteOriginally posted by Ash Quote
I can also understand the frustration shown by all affected by SDM failures.
Nevertheless, it's not worthwhile damning SDM technology altogether.
There are still many satisfied SDM lens users out there and the technology works flawlessly and reliably.
Again, another plug for Pentax to get its act together with making SDM better, and restoring consumer confidence in the technology.
Does Pentax even read this forum? Does Pentax listen to its users at all?

Why do many Sigma and Tamron lenses come with multi-year warranties, while the most high-end Pentax lenses only have a one-year warranty by default? I can't even fathom this; over $1000 dollars for a professional-caliber tool that can fail at any moment and cause a photographer costly downtime. It's like a big slap in the face.

These are exactly the kinds of issues that are making me think twice about buying a DA* 50-135mm. I REALLY REALLY want to buy one, but I'm seriously considering the Sigma and Tamron alternatives due to their multi-year warranty and more reliable auto-focus systems. Pentax' lack of action or statement in this area makes me wonder how seriously they take their customers' concerns.
12-29-2009, 06:10 PM   #11
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Sorry for your troubles.

Whomever does not believe there is an issue is not reading the forums. Seems more than clear to me.

I will never buy into SDM v 1, and even if they do fix it in some subsequent iteration, I'll wait a long time before jumping into those waters. Too bad. I'd love to have the 17-70mm or 16-50mm and 50-135mm.

woof
12-29-2009, 06:19 PM   #12
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Has there been any 17-70 SDM failures ? I only hear the others, but mostly the 16-50 an d the 50-135.
12-29-2009, 06:51 PM   #13
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QuoteOriginally posted by pcarfan Quote
Has there been any 17-70 SDM failures ? I only hear the others, but mostly the 16-50 an d the 50-135.
Yes, I have read some owners had failures on DA17-70/4 too.
12-29-2009, 07:44 PM   #14
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QuoteOriginally posted by GoremanX Quote
But is it somehow possible to fool the camera into using the screw-drive anyways? Perhaps by "hiding" one or more of the contacts? Or would that mess up how the camera treats the lens?
I take you-tape-over-the-SDM-contact-on-the-lens way doesn't work as well?
12-29-2009, 08:06 PM   #15
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QuoteOriginally posted by vizjerei Quote
I take you-tape-over-the-SDM-contact-on-the-lens way doesn't work as well?
That'll just disable SDM, not enable the screw-drive. The camera knows what lens is attached and when to enable/disable the screw-drive. All hiding the SDM contacts would accomplish is make the lens manual-focus only. Same thing if the data contact was taped over, only then it also would disable a bunch of other features.
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