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View Poll Results: Select the option that best describes your agreement with the statement
I have a dual SDM and screw drive lens and I want the ability to choose the focus mechanism. 20258.38%
I am planning on buying a SDM/screw drive lens and I want the ability to choose the focus mechanism. 6919.94%
I will not buy a SDM lens until I have the ability to choose the focus mechanism. 7521.68%
Voters: 346. You may not vote on this poll

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09-14-2009, 02:01 AM   #121
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uh..... yes! my SDM failed on my 16-50 and I had to use it on my k10 with screw drive. It seemed a world of difference in speed (faster). I feel like this should be a simple firmware update....

09-14-2009, 04:05 AM   #122
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Everyone missed my earlier post it seems but I have a screw drive K20D now. The camera has some issues and the SDM has failed in the camera. So I attach an SDM lens and the SDM does not work. Screwdrive is fine. I have 2 K20D's and the other one works as normal.

The non-SDM K20D otherwise is fine and has the latest firmware. The contacts are clean and I can't 'see' anything that would have caused this.
I wish I knew how this happened and could offer a solution to everyone who wanted to turn their K20D's to SD only bodies.
09-16-2009, 09:38 PM   #123
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QuoteOriginally posted by alohadave Quote
Why would you buy an SDM lens and disable SDM?

The SDM lenses that have screwdrives are transitional. As bodies progress, the screw drives are going to go away and all new lenses will be SDM.
Actually, the SDM disables itself against your wishes. That is, it breaks. This is the purpose of this discussion. Also, as it turns out, with some Pentax lenses, unlike Canikon ring motor driven AF systems, SDM is actually quite a bit slower than screw drive. Again, for some lenses. So, if you are in a situation that needs speed you have the option.
09-18-2009, 11:15 PM   #124
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Poll - SDM failures: Pentax SLR Talk Forum: Digital Photography Review


*************final count************** 150 post limit reached

16-50: 20 failures from 56.
50-135: 14 failures from 77.
17-70: Two failures from ten.
200: One from 12.
300: One from 23.
60-250: all good from 13 so far.
55: Eight good copies.

Thank you
Russell

09-19-2009, 03:48 AM   #125
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QuoteOriginally posted by Russell-Evans Quote
I thought it would be good to get some numbers for the people that want a firmware option to disable SDM focusing, hence this will be a poll.

Disabling SDM and using the screw drive focus mechanism provides two things, in the event SDM stops working you still can keep using AF via the screw drive, and second, the ability to use a screw drive TC.

Thank you
Russell
Sorry to tell you, but your poll is worthless - You'd have to include options like
4) I don't care what kind of focusing techlogy is used.
5) I'm aware of the fact that a lens may malfunction, but still I'm going to take the risk and buy it.

Have you considered that the failure may not be caused by the SDM mechanism, but by the clutch that makes the dual focussing possible? Failure rate of SDM only lens is not higher that it is with other brands. The dual focus lens seems to be the problem.
09-19-2009, 03:57 AM   #126
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QuoteOriginally posted by Photomy Quote
Actually, the SDM disables itself against your wishes. That is, it breaks. This is the purpose of this discussion. Also, as it turns out, with some Pentax lenses, unlike Canikon ring motor driven AF systems, SDM is actually quite a bit slower than screw drive. Again, for some lenses. So, if you are in a situation that needs speed you have the option.
Unlike Canikon? Wake up!
Canon has no screw drive lenses. They all use in-lens motor technology. Few L-grade lenses ar lightning fast, but the mainstream is micro-USM (AFAIK the same as SDM) and some EF lenses are terribly slow.
Nikon land has plenty of lenses in screw drive that are moving faster than their newer AF-S versions. For instance the 50mm primes. Before I went for Pentax/Canon combination I tried a D80 with their AF-S 18-200 VR lens. It was substantially slower than K10D with FA80-320. I didn't have opportunity to try other lenses, but it was one of the reasons I bought K10D at that time.
09-20-2009, 08:26 PM   #127
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QuoteOriginally posted by elho_cid Quote
Have you considered that the failure may not be caused by the SDM mechanism, but by the clutch that makes the dual focussing possible? Failure rate of SDM only lens is not higher that it is with other brands. The dual focus lens seems to be the problem.
Got a repair estimate for my 3 faulty SDM lenses
QuoteQuote:
For those who got a "chance" to read my previous posts regarding my 16-50 + 50-135 + 300, all DA* with faulty SDM:
I've got a written estimate yesterday and guess what? All the 3 electric motors should be replaced + their mount..! The 3 of them! Unreal!
Cost of repair is $550... Out of warranty of course. No comment...

I had a conversation with a technician last Friday, he told me that the main cause of faulty SDM AF is a bad mount for the small electric motor. He said a 25 cent (sic) piece of plastic is the reason why my lenses were not working, the mount was slightly moving out of its tiny attachment to the internal body, therefore the electric motors were out of place and unable to rotate the AF ring.
He also told me that in some cases, the electric motor has burnt because of that.
Thank you
Russell

Last edited by Russell-Evans; 09-21-2009 at 06:53 AM.
09-20-2009, 08:36 PM   #128
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QuoteOriginally posted by elho_cid Quote
Failure rate of SDM only lens is not higher that it is with other brands. The dual focus lens seems to be the problem.
There are only two "SDM only" lenses, the DA 17-70mm and the DA 55mm. Neither has sold that well and both are relatively new.

Thank you
Russell

09-21-2009, 04:51 AM   #129
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SDM motor mount

QuoteOriginally posted by Russell-Evans Quote
the main cause of faulty SDM AF is a bad mount for the small electric motor. He said a 25 cent (sic) piece of plastic
Russel, thank You for this valuable detail of information.

We don't know how frequent SDM motor failures are. But with 3 of your lenses fail, it may not be unlikely. Can you estimate #shots with each lens prior to failure (LR count or the like)?

If it is likely I assume that sooner or later, we all see our SDM drives serviced (~180$ repairs obviously). So, I have another question to you:


Did Pentax made a stronger SDM motor mount available, to be used as a replacement part when the lens is serviced, that it doesn't happen again?
09-21-2009, 06:00 AM   #130
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QuoteOriginally posted by elho_cid Quote
Unlike Canikon? Wake up!
Canon has no screw drive lenses. They all use in-lens motor technology. Few L-grade lenses ar lightning fast, but the mainstream is micro-USM (AFAIK the same as SDM) and some EF lenses are terribly slow.
Here's a chart showing the focusing motor tech used in each lens:
http://www.usa.canon.com/app/pdf/lens/EFLensChart.pdf

I have yet to run across a "terribly slow" lens, but then again I have not really played with the consumer zooms... but even the old tech 35/2 and 28/2.8 focus pretty quickly.
10-02-2009, 09:17 PM   #131
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JohnCPentax has said that Pentax USA is now looking into the SDM issue.

Thank you
Russell
10-12-2009, 02:10 AM   #132
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It's been seventeen days since JohnCPentax stated Pentax USA was looking into the SDM failure issue. What do you think? Will we get any information about the issue from Pentax USA?

Thank you
Russell
10-12-2009, 05:22 AM   #133
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I highly doubt it. They would never put anything out in the public that indicates there is a failure issue. Frankly it's probably "within industry standards" for failure %'s anyway and forums/the internet just get all the unhappy people who've had an issue which makes a small problem look huge.

That being said I still want the firmware update for the K10 and K20D!!. Even if they don't make a big splash about it. For me it's a matter of being on a job and having an important lens rendered useless if there's an issue. Because of this I have a backup lens for my DA*16-50mm just in case.
10-21-2009, 08:00 AM   #134
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How sad, people are dumping failing lenses on the marketplace.

https://www.pentaxforums.com/forums/779746-post1.html

Thank you
Russell

edit: The seller posted her side of the story after I posted this, so be sure to read the entire thread.

Last edited by Russell-Evans; 10-22-2009 at 01:47 PM.
10-21-2009, 08:03 AM   #135
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It is Russell and it's equally sad we are not making more of an issue that clearly is not an isolated case. it might not be a flood of problems right now, but how many of these lenses will be working in ten years and then it's too late to reverse the screwdrive debate.

We really need a solution now. I can't see Pentax dropping SD from the bodies, so they need to give us a choice.
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