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Straw Poll - SDM reliability...

John-Paul Treen , Apr 01, 2009; 07:31 p.m.

OK - having read a few things about the SDM motors in Pentax products possibly being a bit less reliable than the old screw drive system (makes sense, a motor is more likely to fail than a driveshaft), I thought it might be an idea to conduct a straw poll to see what peoples' general experience has been with these things. If people with SDM lenses could spare a second and say what SDM lenses they have, how long they've had them, what level of usage they've been subjected to, how much the weather sealing has been tested and whether they've had any problems...
...at the end, if there's sufficient response, I could cobble together some rough stats (not pretending genuine scientific method here, just a rough idea...)
I'll kick off...

DA*50-135 - had it 9 months, used twice or three times a month, used in rain and snow, no issues


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Geoff Francis , Apr 01, 2009; 08:04 p.m.

Don't have any SDM lenses but have plenty of Canon USM lenses, which is the same thing. There are hardly ever any reports of ring USM motor failure in the Canon forum. It make sense as the technology used in these motors is far cleverer and far simpler than traditional arc drive motors.
Based on the design I would expect USM/SDM to suffer from an exceedingly low rate of failure compared to arc drive electrics coupled to a drive shaft.

Geoff Francis , Apr 01, 2009; 08:07 p.m.

wow just read the post a few threads down! Suspect it was a manufacturing defect rather than SDMs being inherently more prone to failure.

Michael Elenko , Apr 01, 2009; 08:39 p.m.

I have owned the DA*50-135mm for about a year. I've taken thousands of shots with it indoors and outside. With the K20D attached it is the one rainy day setup I can trust. Never had a problem.


robert colameco , Apr 01, 2009; 08:49 p.m.

John-Paul, I have had my DA 50-135 for a year and a half. Use it weekly, more than any of my other lenses. No problems.

John-Paul Treen , Apr 01, 2009; 09:00 p.m.

Sounds good so far, I want to know what Javier says though...he puts his kit through a lot :)

Javier Gutierrez , Apr 01, 2009; 09:48 p.m.

Well, I have the DA*16-50, DA*50-135, DA*200 and DA*300 and have never had an SDM problem. I have bought them all pretty much with in a day or two of their release. But in all honesty, I also use them very little.

Justin Serpico , Apr 01, 2009; 10:04 p.m.

I personally believe there is a problem with the dual SDM/slot drive and while I applaud Pentax for not abadoning recent ist and K series buyers, the fact is they should have just went SDM from the start since the release of the SDM lenses was 9 months or more post K10D launch, and Pentax already had more SDM bodies released or pending. Most of the buyers of the 50-135mm were people who needed a higher end lens, and had the income to buy a new body. I am doubtful a lot of 50-135s were mounted to ist DLs and K100D (non supers).

I disagree with Geoff, I have seen reports of in lens motors failing and needed service on both Canon and Nikon. Lindy also comments on how the older USM canon lenses are not servicable anymore.

Do I think this is a reason to not buy the SDM lenses? No, but I've noticed HSM, USM, and AF-S all seem to have shorter working lifes than good old slot drive. I wouldn't hesitate to buy a 10 year old Nikon or Pentax slot drive, even if it was physically beat up, I'd have a hard time buying a similar AF-S/SDM lens.

So this is an instance of being careful what you ask for, don't forget for years the knock on Pentax was that it was the last camera maker without micro motors in the lenses. So old school, so 1990s and such, but the reality is the slot drive lenses seem to last for decades while I bet most of the AF-S, USM, and other micro motor lenses have significantly shorter lives when given the same workload.

So I for one will not EVER complain that it's currently impossible to put an SDM motor into the Limiteds, and those who are complaining might regret it in a few years if the technology does allow it.

Andrew Gilchrist , Apr 01, 2009; 10:38 p.m.

My only SDM lens is a DA17-70/4 and I haven't had it long enough to make any statement about reliability. While the quietness is pretty cool, I don't think it's as nice an addition as the quick-shift focus ring clutch that Pentax managed to implement nicely on drive-shaft AF lenses as well. I'm hoping that whatever lessons Pentax learned with the earlier DA* SDM implementation went into the more recent DA17-70/4 and that I'll be spared some of these gremlins. Fingers crossed. It does seem that Pentax probably should have allowed disabling of SDM in the body firmware so that the dual-drive DA* lenses could be used old-school if desired.

Ken Yee , Apr 01, 2009; 10:59 p.m.

cameralensrentals.com also claim that the Sigma 70-200 HSM is failing a lot more for them than the Tamron...
Geoff: SDM is not the same as USM. SDM is a micromotor...USM is a ring motor w/ less moving parts as I understand it...

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