[originalwinger]

Hi, I have a chance to purchase a DA 50-135 serial number 9009617 and like everyone am concerned about SDM failure. The owner says the box said Ricoh not Hoya although the box is gone so really not sure. Is there any other way of telling from the serial number ? or if it has the updated SDM ?

[sergysergy]

Worst case scenario you can always convert it to screw-drive and forget about the problem.

[originalwinger]

That is always a great backup option although if I pay the price for SDM it would be nice to have.

[AlwaysAl]

Hi, I have a chance to purchase a DA 50-135 serial number 9009617 and like everyone am concerned about SDM failure. The owner says the box said Ricoh not Hoya although the box is gone so really not sure. Is there any other way of telling from the serial number ? or if it has the updated SDM ?

Bought mine used (9006658) 2014 with invoiced proof of a motor replacement. At first, worked great then motor failed (within the year...as per bad luck norms, repair warranty had time-expired), Thinking the motor problem would have been resolved with newer motors, (and trying tp keep it functionally original), replaced second motor @ Sun. That motor failed also in a little over a year. A side discussion indicated there'd been no revision to a replacement motor for this lens.. Converted lens to screw drive and now is a favoured lens. Looking back, if I had to do it again, wouldn't have wasted time on the motor replacement...if it fails, convert. It's a great lens either way.

[7.62lew]

I bought one used on the forums and have had no issues with the sdm. It is one of my favorite lenses. If mine ever did fail I would covert to screw drive.

[Wingincamera]

I purchased my 50-135 used a few years ago, SN# 9305678, and have had no problems with it. Purchased off of E-bay.

[UncleVanya]

I have a theory about repeat failures of sdm. I suspect lenses with repeated failures have something else wrong that loads the motor with additional drag or something that causes the failures.

My own 50-135 was purchased with non-working sdm that was supposedly refurbished but not working. I got it working and it has never failed me in the many years since. But if it failed I would convert it and not worry a bit.

[StigVidar]

I have a theory about repeat failures of sdm. I suspect lenses with repeated failures have something else wrong that loads the motor with additional drag or something that causes the failures.

I believe it is wear and some motors was made that wear out faster than expected.

https://en.wikipedia.org/wiki/Ultrasonic_motor

[originalwinger]

Bought mine used (9006658) 2014 with invoiced proof of a motor replacement. At first, worked great then motor failed (within the year...as per bad luck norms, repair warranty had time-expired), Thinking the motor problem would have been resolved with newer motors, (and trying tp keep it functionally original), replaced second motor @ Sun. That motor failed also in a little over a year. A side discussion indicated there'd been no revision to a replacement motor for this lens.. Converted lens to screw drive and now is a favoured lens. Looking back, if I had to do it again, wouldn't have wasted time on the motor replacement...if it fails, convert. It's a great lens either way.

That’s the tough thing about that lens, the answers are all over the map. Either no failures or just buy it and convert it if problems, decisions decisions decisions. If the asking price was reasonable I would go for it but in this case I may be best to wait. Thanks for your responses.

[caliscouser]

Hi, I have a chance to purchase a DA 50-135 serial number 9009617 and like everyone am concerned about SDM failure. The owner says the box said Ricoh not Hoya although the box is gone so really not sure. Is there any other way of telling from the serial number ? or if it has the updated SDM ?

Almost certainly a 2007 build (pre-2012 when the SDM redesign occured).

However it is a beautiful lens, one of my favorites. The SDM thing is a lottery. You just have to accept that as a price of admission.

[bschriver11]

I'm not so sure the SDM is better than the screw drive other than being quieter? It sometimes hesitates to focus and i don't see any speed advantage over my screw drive lenses. Maybe some input from those who have converted might be helpful here? Great lens though either way.

[UncleVanya]

I believe it is wear and some motors was made that wear out faster than expected.

https://en.wikipedia.org/wiki/Ultrasonic_motor

I’ve converted a large number of lenses. The lenses that customers have told me have had multiple failures look no different from those with only one failure or mine with one known failure; factory refurbishment and no failures since. It seems unlikely that a lens would have multiple replacement motors fail multiple times unless there is something outside the motors that contributes to this. You would think replacement would reset the luck of the draw - and yet we have reports of three failed motors in multiple lenses. And others with no failures at all. And failures seem to occur fast with some lenses. 1-2 years while others have lenses for a long time without incident.

[morenjavi]

Hello.
I bought one used several years ago, S/N 92299XXX. I read that lenses without issues have S/N starting at 923XXXXX, but I can't remember where I read it.
Mine started to fail maybe one or 1,5 years after I bought it. But mine doesn't have a total fail, it's just that is needs to 'awake'. So If I need to use ir, I need 2-3 mins pointing to a light source and trying to focus. After some time the motor just starts to work, then I made some focusing tests from near to far, and then I can use it during the rest of the day.
I made the conversion one time but didn't like the noise at all, so I re-converted to SDM again.
After several years of use I still have the issue with SDM, but as I told, it's not fully broken.
It's maybe my favourite lens, by the way.

Good luck.

[tibbitts]

I bought a used copy here which still uses SDM, and have been happy with it overall because it isn't decentered (my main criteria for happiness with lenses.) But it can't (PDAF) autofocus within the ridiculously tiny +/-10 adjustment range of any of my cameras. And if it did I'm not convinced (just based on experience with other lenses) that it would be accurate at all the focal length settings. However being f2.8 I can focus manually (or CDAF) in most static situations. Honestly I can't get any of my bodies and lenses to focus reliably in circumstances when I really need AF. AF was fine even back in the K100 era when I had slower lenses and almost always used small apertures. Now that I have f2.8 lenses and occasionally want to use wider apertures (say, f2.8 or f4), not so much.

[morenjavi]

I bought a used copy here which still uses SDM, and have been happy with it overall because it isn't decentered (my main criteria for happiness with lenses.) But it can't (PDAF) autofocus within the ridiculously tiny +/-10 adjustment range of any of my cameras. And if it did I'm not convinced (just based on experience with other lenses) that it would be accurate at all the focal length settings. However being f2.8 I can focus manually (or CDAF) in most static situations. Honestly I can't get any of my bodies and lenses to focus reliably in circumstances when I really need AF. AF was fine even back in the K100 era when I had slower lenses and almost always used small apertures. Now that I have f2.8 lenses and occasionally want to use wider apertures (say, f2.8 or f4), not so much.

I've suffered front or back focusing with most of my lenses since I bought my first Pentax Camera, the *ist DS.
Maybe the lens with the worst focusing behaviour is my tamron 28-75mm, that optically is still a great lens. My problem with this lens is that you need different focusing corrections depending on focal length. That is, at tele end I need to correct for front focusing, but and the wide end I need to correct for back focusing. But it's still worse, because the focusing behaviour changes when you set the diaphragm to f5,6 or more. Starting at f2,8 you need one adjustment, but at f5.6 and above you need another. At f5,6 you can use this lens with just one single focusing correction for all the focal lengts, but when I planned to use this lens at f4,0 or so, I needed a focusing correction for f<5,6 and focal length in the range 50-75mm.

Maybe 3rd party lenses are worse related to focussing accuracy. Also I think that primes are 'better' related to focusing accuracy. I only have one prime with AF, my FA50/1,7. This lens only needs one adjustment and it focuses fine at any apperture, but my other lenses seems to 'shift' the focus a bit when you reach f5,6, compared to f5,0 and below.
Then there is the AF point accuracy, that is f5,6 for old Pentax bodies, maybe related to the different focusing adjustments above or below f5,6 ?

When I bought my K3-II, focussing accuracy was improved too, specially if I use the central AF points (f2,8 accuracy). My Tamron lens focuses way better on my K3-II compared to the K5.
But I still need to set different focusing corrections depending of the apperture for some lenses. As an example, my sigma 17-50mm needs -4 or +4 depending on the apperture, and my 50-135mm needs +2 or -2 (not a lot, really).

It seems the new K3-III have improved focusing accuracy a lot, is finally Pentax at the same level compared to other brands? I see reviews of many modern cameras that offer eye detection and I admit that I feel a bit envy.

Regards.