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07-13-2015, 12:10 PM   #1
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DA* 200 and 300 screwdrive conversion

I successfully (and easily) converted my DA* 200 and DA* 300 lenses to screwdrive. I was curious about this and my searches only yielded conversions for the DA* 16-50 and DA* 50-135. The AF on my 200 and 300 work fine, but I was still curious. Partially since my 16-50 and 50-135 needed to be converted and the screwdrive AF works noticeably better on those lenses. The conversion on the 200 and 300 was successful, but I preferred the SDM on those lenses so I switched it back to SDM. Just wanted to let people know that the conversion is possible (in the case of a dead SDM) on these lenses and was similar to the 16-50/50135, changing the C0 value to 80, just less of them to change in the file (I'm guessing because they are primes compared to zooms). I don't have a 60-250 to test this on but I would think that it would be similar? Just wanted to share that with everyone in case someone had a dead SDM on their 200 or 300, though they aren't as prevalent as the 16-50/50-135 SDM motors going bad.

07-13-2015, 12:32 PM   #2
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Can this be done with any Pentax DSLR? And how?
07-13-2015, 01:55 PM - 1 Like   #3
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QuoteOriginally posted by stillshot2 Quote
Can this be done with any Pentax DSLR? And how?
I did it with a K-5 (no luck with my K-3). I believe K-5 and earlier models can do it. The files required to access the debug may vary.

You can check out the thread for more info: https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/208353-how-...m-f-2-8-a.html

It's a long thread at this point so may require some searching for the proper files to create for your camera.

Last edited by transam879; 07-13-2015 at 04:37 PM.
07-13-2015, 03:46 PM   #4
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Great news!

07-14-2015, 11:38 AM   #5
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does NOT work with 60-250. At least, not with any instructions out there for the other lenses. You end up with the SDM and screw drive fighting or something and it won't focus reliably at all.
07-14-2015, 05:27 PM   #6
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QuoteQuote:
I did it with a K-5 (no luck with my K-3).
Thanks for the info. Darn. I only have a k-3 and my DA300 sdm has died for the third, and I expect final, time.
11-03-2017, 05:54 PM   #7
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So any experiences about AF performance after conversion to screwdrive?
07-03-2018, 10:14 AM   #8
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Anyone with experience of AF speed between SDM and screwdrive on DA* 300 ?

07-03-2018, 12:08 PM   #9
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I've converted both lenses several times. But once they reach me they are typically dead already as far as SDM. I own the DA* 200 and it seems about the same maybe slightly faster in screw drive but that could be some wishful thinking. I keep mine SDM however as it has no known issues. The FA* 300 I have seems similar to the DA* 300's in terms of focusing in screw drive but I couldn't swear to it.
07-04-2018, 02:22 PM   #10
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QuoteOriginally posted by angerdan Quote
Anyone with experience of AF speed between SDM and screwdrive on DA* 300 ?
I have converted mine.

The reason I did so is that on my K3 I was getting less reliable focus lock in lower light than with my Bigma. Really shouldn't happen with a faster/sharper lens.

Focusing speed is hard to judge but seems ok. I will swap back sometime to see if I made a mistake.

Edit: Just to clarify, focus lock is better in screw drive.
07-04-2018, 04:01 PM   #11
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QuoteOriginally posted by alfa75ts Quote
I have converted mine.

The reason I did so is that on my K3 I was getting less reliable focus lock in lower light than with my Bigma. Really shouldn't happen with a faster/sharper lens.

Focusing speed is hard to judge but seems ok. I will swap back sometime to see if I made a mistake.

Edit: Just to clarify, focus lock is better in screw drive.
My guess is that your SDM was / is failing. I have had a customer send me a 50-135 that had very bad focus lock ability and post conversion it was perfectly fine. I compared it to my 50-135 which has no SDM issues before conversion. It would work in great light but not poor light. After conversion it was no trouble at all.
07-04-2018, 04:33 PM   #12
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QuoteOriginally posted by UncleVanya Quote
It would work in great light but not poor light.
But the question is why?

Can't be the lens on it's own, even if the SDM is failing, it doesn't care how much light there is.

So in part it must be how the camera drives the SDM in lower light. Does it drive it faster, assuming it's way out of focus, and therefore keep over-running the focus point (hunting).

Then again, is it hunting or is it trying to move the focus and failing? But then, why would the amount of light matter?

It's a puzzle. But the conversion helps, so that's what I did.
07-04-2018, 07:35 PM   #13
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QuoteOriginally posted by alfa75ts Quote
But the question is why?

Can't be the lens on it's own, even if the SDM is failing, it doesn't care how much light there is.

So in part it must be how the camera drives the SDM in lower light. Does it drive it faster, assuming it's way out of focus, and therefore keep over-running the focus point (hunting).

Then again, is it hunting or is it trying to move the focus and failing? But then, why would the amount of light matter?

It's a puzzle. But the conversion helps, so that's what I did.
It did NOT hunt. It seemed to just give up. It was as though the camera was expecting some changes none happened or they were too subtle and it gave up.
07-04-2018, 07:38 PM   #14
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QuoteOriginally posted by UncleVanya Quote
It did NOT hunt.
Ok, mine did.
07-04-2018, 07:40 PM   #15
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QuoteOriginally posted by alfa75ts Quote
Ok, mine did.
Interesting. Yours did what most do then. This lens was strange since it seemed fine until the tough focusing situations popped up. Then it just gave up. Well sorry for the red herring.
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