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6 Days Ago   #31
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QuoteOriginally posted by ChristianRock Quote
Thank you, that was very informative.

I guess sticking with screw drive and learning to live with its limitations in focusing time, is the best approach. The upside is reliability and great images

The two seem to focus at about the same speed on a good working sdm lens. The failing sdm lenses are much slower.

As for reliability, I don't know what I would decide about the da* 50-135 I have. It has been quite reliable in sdm mode. However before a long trip where I'd be away from a body that could convert it for an extended time, I might just go ahead and convert to avoid potential impact on a trip.

5 Days Ago   #32
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QuoteOriginally posted by UncleVanya Quote
The two seem to focus at about the same speed on a good working sdm lens. The failing sdm lenses are much slower.

As for reliability, I don't know what I would decide about the da* 50-135 I have. It has been quite reliable in sdm mode. However before a long trip where I'd be away from a body that could convert it for an extended time, I might just go ahead and convert to avoid potential impact on a trip.
Well I guess that for you, you could do it blindfolded now, so you can just convert it and then convert it back...
I have a K10D so I was curious about checking to see if my 16-50 was dead or just failing, but if the failing SDM is slower than the screw drive, I'll just leave it as is. The screw drive is a bit annoying because it keeps being noisy while it's undecided on focus, but for what I paid for the lens, I won't complain at all, the images I get from it might not be as sharp as a prime sometimes, especially at wider apertures, but they do have great rendering and colors. I'm loving the lens and don't think I'd be happier with the Tamron or Sigma equivalents even if they might be sharper...
5 Days Ago - 3 Likes   #33
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QuoteOriginally posted by ChristianRock Quote
Well I guess that for you, you could do it blindfolded now, so you can just convert it and then convert it back...
I have a K10D so I was curious about checking to see if my 16-50 was dead or just failing, but if the failing SDM is slower than the screw drive, I'll just leave it as is. The screw drive is a bit annoying because it keeps being noisy while it's undecided on focus, but for what I paid for the lens, I won't complain at all, the images I get from it might not be as sharp as a prime sometimes, especially at wider apertures, but they do have great rendering and colors. I'm loving the lens and don't think I'd be happier with the Tamron or Sigma equivalents even if they might be sharper...
In my experience... I've seen several lenses that customers sent with "working" sdm that wasn't working well. Problems focusing on low light or low contrast, problems where the lens took too long to focus etc. In all of those cases (maybe 5 in all) the issues were completely resolved by conversion. The first time this happened I had been skeptical and told the customer we could try it. After that success I told others with similar issues what had happened and they sent lenses my way and we confirmed that it worked.

I did have one lens that wouldn't convert. That lens arrived unable to manually focus so I wasn't surprised it failed, something else was wrong inside that lens.

On the other hand... My own 50-135 was purchased from an eBay seller who cleared out a large lot of stuff in the area near where Pentax USA had been. It is rumored that these were items sold off from that hq which had also been a service center long ago. I tried a trick I read about to see if I could wake up the sdm guessing it might have been a refurbished unit that just hadn't woken up when tested. My trick worked and the lens has never given me any issues since then. The middle of the story use that you can try sdm covering the lens you have and if it doesn't work well enough convert it back to screw drive.

Last edited by UncleVanya; 5 Days Ago at 08:18 AM.
4 Days Ago   #34
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As a person who buys second hand glass this topic definitely gives me pause. Do we know what date ranges on what lenses are most effected, or is this a problem through to recent manufactured lenses?

4 Days Ago   #35
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QuoteOriginally posted by ALLCAPS Quote
As a person who buys second hand glass this topic definitely gives me pause. Do we know what date ranges on what lenses are most effected, or is this a problem through to recent manufactured lenses?
Not really. There were discussions of redesigned motors, but some people had lenses beer that failed and older that just worked great.

I wouldn't get too worried. I will also assert that the DA* 200, 300, and the 60-250 are likely the least impacted based on questions asked of me and lenses I have converted.
4 Days Ago   #36
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QuoteOriginally posted by UncleVanya Quote
I will also assert that the DA* 200, 300, and the 60-250 are likely the least impacted based on questions asked of me and lenses I have converted.
Doe the DA* 55/1.4 make the list?


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4 Days Ago   #37
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QuoteOriginally posted by stevebrot Quote
Doe the DA* 55/1.4 make the list?


Steve
No clue. Not a lens that can be converted so I rarely get contacted about it. Mine worked great and always has. I feel comfortable saying the da 60-250 is rarely impacted because a few people have contacted me about it assuming it could be converted due to the dual focus systems, and I've seen threads on rare occasions asking for help on converting this lens but my overall impression is that these failures are rare. Most users aware of my service don't know that the 60-250 isn't able to convert. So the scarce number of inquiries seems useful data. The da 55 most know lacks screw drive so few people assume I can do anything to it. Thus the lack of inquiries isn't as diagnostic. But I will say it seems low.
4 Days Ago   #38
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QuoteOriginally posted by UncleVanya Quote
Not really. There were discussions of redesigned motors, but some people had lenses beer that failed and older that just worked great.

I wouldn't get too worried. I will also assert that the DA* 200, 300, and the 60-250 are likely the least impacted based on questions asked of me and lenses I have converted.
Just for the statistics: I converted a DA* 300.

3 Days Ago   #39
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QuoteOriginally posted by UncleVanya Quote
I tried a trick I read about to see if I could wake up the sdm guessing it might have been a refurbished unit that just hadn't woken up when tested. My trick worked and the lens has never given me any issues since then. The middle of the story use that you can try sdm covering the lens you have and if it doesn't work well enough convert it back to screw drive.
What's the trick?
3 Days Ago   #40
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QuoteOriginally posted by leekil Quote
What's the trick?
Well... It sounds nuts and I don't know where I read it at least not right now. With the camera in manual focus mode and the lens in manual focus mode you rapidly spin the focus ring back and forth for several minutes. I held the lens focus ring with one hand and the camera body with the other and rapidly counter rotated them. I think when it works it is replicating the screwdriver trick to release stuck sdm. After a few minutes I switched back to af and it all just worked. That was many years ago. The lens has remained fully functional. I had a couple of customers I shared this story with ask for me to try on their completely dead sdm lenses. I've had one or two wake up but both were slow and seemed weak. The customers asked for me to finish the conversion. So I don't know if this works for more than a handful and it might be dangerous to try so I don't recommend it. In my case there was reason to think that the sdm had been replaced but wasn't working when tested by the seller. I reasoned that it might be stuck on some poorly tolerenced part that could be moved until it was lower friction if I was lucky. I was lucky but my confidence in this method is pretty limited.
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