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06-16-2013, 09:18 AM   #16
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QuoteOriginally posted by carrrlangas Quote
You should know your DA16-50 is now in Argentina (I bought it from icywindow). Works great and no SDM possible failure is important because there is no way of fixing it locally. You dont have a DA50-135 or DA60-250 youve converted and willing to sell?
SDM is not that only thing that can fail.
There are also reports that the whole AF mechanisme (gears, shafts) fails, Pentax actually suggest that's the reason some SDM break.

Pentax never should have 3 focusing systems inside a lens, it;s far to comeplicated. I;m happy they have reported not to do that anymore.

06-16-2013, 10:22 AM   #17
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QuoteOriginally posted by Anvh Quote
Pentax never should have 3 focusing systems inside a lens, it;s far to comeplicated. I;m happy they have reported not to do that anymore.
I guess you mean 3 focusing mechanisms? SDM, Screwdrive and which would be the third, quickshift?
Why is it complicated? SDM circuit has nothing to do with screwdrive mechanism, they run independently. Now, quickshift, I am not sure and this is where I suppose you are right. Ive read about some DA50-135 that could not be manually focused and SDM had broke
06-16-2013, 10:28 AM   #18
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Screwdrive, in lens focus and manual focus.

The gears all end up at one point though.
They all have a clutch but if for example the clutch fails then you've a problem, nothing will work then since the lens can't move anymore.
That's why the SDM did not work anymore in your story.

Here you can see that the SDM motor and the screwdrive power all go into one shaft to the front where the manual focus is. If that shaft locksup then it's game over.
http://bangmedia.no/pentax/sdmfix/

Last edited by Anvh; 06-16-2013 at 10:34 AM.
06-16-2013, 11:25 AM   #19
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SDM problems largely overblown...

I'm not going to spend much time on this because you can find upteem posts and polls on it already, but:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/83743-sdm-sile...s-failure.html

If you go to the above poll, you'll find basically no reports of problems with the 17-70sdm (just a couple, which can be any problem with any lens), the DA300, the DA200 or the DA60-250. The problems, of any significant number, have all been with the 50-135 and the 16-50, and even in those cases, the reported non-problems outnumber the reported problems by 3:1. It is often noted that people who experience problems are more likely to answer polls on the subject that those who do not experience problems. So the poll data actually favors an anti-sdm bias.

For my experiences, i own the DA50-135, the DA300 and the DA17-70. I'm fond of all 3 lenses and have not experienced any sdm problems with any of them. The DA50-135 i couldn't do without. Its responsible for the majority of the 25 pictures i sold in the last 12 months - a very useful range for me.

There's another poll that Adam did to show the number of complaints regarding sdm by year. It shows that complaints have been falling off rapidly in 2011 and 2012. And some Pentax official that Adam talked to said the sdm problem was resolved in a more recent interview. Another thread that came up in my search was a comparison between lens problems reported by lensrentals or some such company for all brands they carry. There isn't a lens brand out there that hasn't had repair problems for one model of lens or another. And that statement includes Sigmas HSM drive.

06-16-2013, 06:50 PM   #20
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The grass just looks greener on the other side.
Thats because we usually don't eagerly seek out info about lens issues on other systems.

I've been through that (on Canon)
Do a search on 'Err01' and see that this lens communication issue happens on many Canon lenses even 'L' s
The worst thing being that the lens cannot function at all when such failure happens since even the aperture relies on the lens communication.

Like what others have suggested, maybe you want to convert your lens to screw drive.
Or wait till it fails to think about that route.

BTW, when ppl say their lens is 'dying' its usually intermittent issues usually dirty contact pins or recessed pins and not true SDM failure which is sudden.
You may want to check this out too.
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