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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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02-15-2010, 02:25 PM   #196
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I beleive this is a SDM motor

Google Translate
QuoteQuote:
Hello to all holders of 16-50, repaired my lens today, replaced gear plate a assy (Do not know how it is translated).
Стоимость ремонта 5950р, 2000р работа и 3950р сама запчасть, гарантию дали 6 месяцев.
The cost of repairs 5950r, 2000P work and 3950r spare itself, a guarantee was given 6 months.





Thank you
Russell



The discoloration is interesting on only the one gear. I think that would rule out lubricant.

Thank you
Russell

02-15-2010, 04:13 PM   #197
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Interesting. Thanks for the post with pictures Russel. See the ring with the "flutes" in it? That, I believe is the SDM stator. The picture is a great example of why ring-USM is so much better. If you look at a ring-USM lens, that stator is larger than the lens inner diameter, and extends completely around the lens housing. That is why ring-usm is so much faster as well as more reliable. You can get very large values of torque, with no gear mechanism required. The gearing adds complexity and multiple potential points of failure. It also appears in your photo, that the gear drive makes use of nylon gears. The advantage of nylon gears is that they are quiet. The disadvantage, is that they are less reliable than metal gears, and the typical failure if the gear jams, is for the teeth to break off. For a metal gear train, typically the motor will stall if the gear jams, resulting in no failure of the gears.

True ring USM is beauty in simplicity. The picture below is the entire focusing motor system for an EOS ring-USM. For scale, remember that ring goes around the entire lens. No gears necessary.



For some reason this site seems to block the pic. Here is the link just in case:
(scroll to figure 2)
http://www.photoscene.com/sw/tour/inside.htm

I wish Pentax would do the same thing.

Last edited by PentaxPoke; 02-15-2010 at 04:23 PM.
02-15-2010, 05:04 PM   #198
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QuoteOriginally posted by Russell-Evans Quote
The discoloration is interesting on only the one gear. I think that would rule out lubricant.
Very interesting. Thanks for the links.

QuoteOriginally posted by PentaxPoke Quote
I wish Pentax would do the same thing.
Same here. Even Sigma has (big) ring motors, not these baby ring motors.
02-16-2010, 10:10 AM   #199
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Re: I believe this is a SDM motor

It would be helpful, if some questions could be answered, e.g.:

Which was the faulty part in the assembly (see citation below)?
Was the whole unit (as shown) replaced?
If not, were these photos taken before or after repair?
Is there an obvious difference between the parts (old/new)?

Could somebody pose these questions in the Russian (<- main problem) forum?



Rumor:
QuoteQuote:
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 cts 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.
Got a repair estimate for my 3 faulty SDM lenses ....: Pentax SLR Talk Forum: Digital Photography Review

02-16-2010, 10:22 AM   #200
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QuoteOriginally posted by PentaxPoke Quote
It also appears in your photo, that the gear drive makes use of nylon gears. The advantage of nylon gears is that they are quiet. The disadvantage, is that they are less reliable than metal gears, and the typical failure if the gear jams, is for the teeth to break off. For a metal gear train, typically the motor will stall if the gear jams, resulting in no failure of the gears.

True ring USM is beauty in simplicity. The picture below is the entire focusing motor system for an EOS ring-USM. For scale, remember that ring goes around the entire lens. No gears necessary.
Anyd it looks like the screw drive is all metal gearing.....
Actually it may be more motor and mount failures then the gears.. they are tougher then most think and probably close to the strength (at this size) of sintered metal gears but cut gears would be best (and most expensive..
QuoteOriginally posted by PentaxPoke Quote
I wish Pentax would do the same thing.
See their new patents
02-16-2010, 10:38 AM   #201
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SDM failed me, but Pentax remedied the problem QUICKLY

I bought a 50-135 DA* from Wolf Camera Clearance center recently. At first, the SDM didn't work with my K7. I used the lens on my K10D a little before I switched to the newer firmware. After repeated tries, it finally started working, on both cameras.

However, I shot a wedding two weeks ago and the SDM failed in low light. It was squeaky, slow and hunted a lot. I sent it to the warranty service center and they had it back to me in EIGHT DAYS! Very fast service. It works great now, and I'm happy with that.

My 16-50mm has always worked beautifully. But I'm with you...I'd rather be able to select the screw drive if SDM fails. Do you think they'll do that?
02-16-2010, 11:44 AM   #202
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QuoteOriginally posted by jeffkrol Quote
Anyd it looks like the screw drive is all metal gearing.....
Actually it may be more motor and mount failures then the gears.. they are tougher then most think and probably close to the strength (at this size) of sintered metal gears but cut gears would be best (and most expensive..
Yes the screw drive input side looks metal, but it appears to me that the output side is nylon. I don't know exactly how that part fits onto the lens, but if I had to guess, the nylon gear that is on the SDM drive, and the nylon gear that is on the SD side both probably mesh with a common gear on the lens drive. That way, SDM or SD can turn the lens drive.

QuoteOriginally posted by Green Chile Quote

I'd rather be able to select the screw drive if SDM fails. Do you think they'll do that?
There are 697 people that are asking for the same thing: http://www.petitiononline.com/mod_perl/signed.cgi?593039&1
02-16-2010, 02:27 PM   #203
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I tallied up the lens numbers in the DPR posts.

http://spreadsheets.google.com/...key=tytSIc_52GQo_jdEMXdcEmg&output=html


edit: added a few that were missed.
By my count, there are 75 lenses with SDM issues reported by 61 individual posters. Of the 61 posters, there was enough information in 22 of the posts to determine that the poster had at least one other SDM lens that worked fine on their camera. Only 10 posters out of the 61 reported multiple SDM issues.

16-50mm, 32 lenses reported
50-135mm, 31 lenses reported
edit: 17-70mm, 5 lenses reported
200mm, 2 lenses reported
300mm, 5 lenses reported


Thank you
Russell


Last edited by Russell-Evans; 02-22-2010 at 02:44 AM.
02-16-2010, 02:44 PM   #204
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QuoteOriginally posted by Russell-Evans Quote
I tallied up the lens numbers in the DPR posts.

http://spreadsheets.google.com/...key=tytSIc_52GQo_jdEMXdcEmg&output=html


By my count, there are 70 lenses with SDM issues reported by 60 individual posters. Of the 60 posters, there was enough information in 21 of the posts to determine that the poster had at least one other SDM lens that worked fine on their camera. Only 8 posters out of the 60 reported multiple SDM issues.

16-50mm, 32 lenses reported
50-135mm, 27 lenses reported
17-50mm, 4 lenses reported
200mm, 2 lenses reported
300mm, 5 lenses reported


Thank you
Russell
Wow! Nice work. I think you mean 17-70. Also, there have been reports on the 60-250 (but maybe not in this thread?)
02-16-2010, 06:08 PM   #205
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QuoteOriginally posted by PentaxPoke Quote
I think you mean 17-70. Also, there have been reports on the 60-250 (but maybe not in this thread?)
I did mean the 17-70mm. I'm only counting posts from one site as there may be other people like me that post to multiple places. This would lead to double counting.

If there is someone that wants to be added to the list, just add a post to this DPR thread and I will collect your data.

Thank you
Russell
02-16-2010, 07:34 PM   #206
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QuoteOriginally posted by PentaxPoke Quote
Yes the screw drive input side looks metal, but it appears to me that the output side is nylon. I don't know exactly how that part fits onto the lens, but if I had to guess, the nylon gear that is on the SDM drive, and the nylon gear that is on the SD side both probably mesh with a common gear on the lens drive. That way, SDM or SD can turn the lens drive.
I would guess that you are correct, the systems seem to be virtually independent but for a common point of drive on the lens (driving the focus helicoid). I would assume that the quick focus clutch is mech is part of the larger gear in the screw drive train, pity they can't be retrofitted to DA* lenses, or can they? hmmm. ;-)
04-05-2010, 04:25 PM   #207
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I would support having the option to choose the screw drive option in the event of SDM failure.

I have the 16-50mm and it's been to Pentax for motor replacement once already. Came back fine. Now, 2 months later, the SDM was moving slowly this morning - started working eventually. This is how the motor failed last time - and will be out of warranty now.

So - instead of a $700 non-automatic focusing lens with SDM failure, I'd like the option to have a slightly noiser, but auto-focusing lens via the screw drive. It's a shame that all of that glass hinges on the long term performance of a small but troublesome focusing motor.
04-05-2010, 04:59 PM   #208
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QuoteOriginally posted by Russell-Evans Quote
I tallied up the lens numbers in the DPR posts....

edit: added a few that were missed.
By my count, there are 75 lenses with SDM issues reported by 61 individual posters. Of the 61 posters, there was enough information in 22 of the posts to determine that the poster had at least one other SDM lens that worked fine on their camera. Only 10 posters out of the 61 reported multiple SDM issues.
...
If the responses on Pentaxforums/DPreview is but a sampling of the number of Pentax SDM lenses users globally, the fact remains that this tally seems like a very small number of respondents, considering the thousands of SDM lenses that Pentax has sold worldwide...

We got one of the biggest Pentax users in one place where I am and the number of SDM failures that we roughly know of from users who we know in person, and from our local Pentax repair technician, is extremely low.
I'll let everyone draw their own conclusions whether this problem has been overblown or not.

Last edited by creampuff; 04-05-2010 at 05:05 PM. Reason: spelling
04-06-2010, 06:27 AM   #209
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QuoteOriginally posted by creampuff Quote
I'll let everyone draw their own conclusions whether this problem has been overblown or not.
If you're like me and had to save up to buy the DA* 50-135 (not a cheap lenes), expecting to get a Pentax QUALITY product and the autofocus failed at 13 months, (timed perfectly with losing my job and needing to hold back on spending), you would not think this problem is overblown.
04-07-2010, 12:41 AM   #210
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QuoteOriginally posted by creampuff Quote
If the responses on Pentaxforums/DPreview is but a sampling of the number of Pentax SDM lenses users globally, the fact remains that this tally seems like a very small number of respondents, considering the thousands of SDM lenses that Pentax has sold worldwide...
Like here, DPR may have 16000 members, but only a few hundred are actually posting. 60 some people out of a few hundred? 60 people is 1% of 6000, 60 is 10% of 600.

Or look at it as lenses, 75 is 1% of 7500, 75 is 10% of 750. Do you think there are 7500 SDM lenses owned by the people that post at DPR? Do you think there are 750 SDM lenses owned by the people that post at DPR?

Although I used 1%, I personally think a 0.1% is the acceptable number, 75 is 0.1% of 75000. Do you think the are 75,000 SDM lenses owned by the posters at DPR? 60 is 0.1% of 60,000. Do you think there are 60,000 people posting to the Pentax forum at DPR?

QuoteOriginally posted by creampuff Quote
We got one of the biggest Pentax users in one place where I am and the number of SDM failures that we roughly know of from users who we know in person, and from our local Pentax repair technician, is extremely low.
I'll let everyone draw their own conclusions whether this problem has been overblown or not.
From the photos that have been posted of the Singapore group, it looks like you have about 50 people. How many SDM lenses are owned?

1% of 100 is 1, 10% of 100 is 10.

1% of 50 is 0.5, 10% of 50 is 5.

1% of 25 is 0.25, 10% of 25 is 2.5.

1% of 10 is 0.1, 10% of 10 is 1.

So do you have a sample size of 100 lenses? If you have 100 lenses, then you could say the issue is less than 1%.

If you had a sample size of 1000 lenses you could then say the issue is less than 0.1%

With a sample size 25 or under, it could just be luck. One or two SDM lenses not failing in 25, I don't think that would be a good bet when there are other larger samples that show an issue. At least we do know there are more than 100 lenses on DPR and here.

I think a lot of the complaints wouldn't even come to light in places that have longer warranties. It seems those with the one year warranties are the people that post, "whew, my lens failed, but thankfully it is under warranty", or "Crap, my lens failed and the warranty just expired". The others are mostly, "my lens failed and the warranty repair is taking months", or "my lens failed and the repaired lens failed". That leaves a lot of room under the bridge for failed lenses not to be reported.

It is your money, spend it as you want. I personally think you better have or buy an extended warranty.

Thank you
Russell

Last edited by Russell-Evans; 04-26-2010 at 11:42 PM.
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