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02-18-2020, 02:49 AM   #1
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SDM to screwdrive conversion?

l watched a Youtube video on this. lf it can be done with a software/firmware upgrade, how is it possible? The only way l can think of is if the lens was built to be either or. ls that correct?

02-18-2020, 03:11 AM - 2 Likes   #2
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QuoteOriginally posted by camera_nut Quote
l watched a Youtube video on this. lf it can be done with a software/firmware upgrade, how is it possible? The only way l can think of is if the lens was built to be either or. ls that correct?


Not an issue I've had to deal with ... yet


I'm fairly sure that these lenses are "either/or" so's they will work on earlier bodies that don't have the power contacts in the lens mount. The "problem" is that they default to SDM when fitted to a capable body and need to be "re-prioritised" so's they default to screw-drive.
02-18-2020, 05:08 AM - 1 Like   #3
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Correct, the first-generation Pentax SDM lenses can also work with the camera's screw-drive motor, for bodies that don't support SDM focusing.

I recently did my first conversion myself. Quite easy, and reversible.

Lots of discussion on this forum thread.

For those who don't want to do the conversion themselves, or who don't have access to a suitable camera body (has to be K5-II or older), forum member UncleVanya offers a conversion service in the forum marketplace.
02-18-2020, 06:51 AM   #4
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There are 5 premium lenses DA* 16-50, 50-135, 200, 300, & 60-250 that were built at the introduction of the in lens motors by Pentax. Each of these has both screw drive and sdm. The implementation has the lens tell the camera if it is sdm or not. If the camera supports sdm, it will only use sdm even if the lens motor isn't working.

The modification reprograms the lens so it doesn't announce itself as sdm capable. All of the above lenses EXCEPT the 60-250 can be converted this way. The 60-250 fights itself when converted, randomly using sdm and screw drive and generally failing to work. So effectively only four of these lens models can be converted.

Since the lenses are all premium models, and sdm failures aren't uncommon*, conversion is popular.

* Rates of failure are unknown. However some people have suffered multiple failures of sdm after repairing lenses the standard way.

02-18-2020, 10:08 PM   #5
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I've been reading this and all the earlier thread with great interest, having just got my hands on a DA* 300 to allow me to get back out with the camera a bit sooner after shoulder surgery, than I would if using the DFA 150-450.
Does anyone here (Australia) provide a service to do the SDM to screw drive conversion?
I would probably have a try at it myself if necessary, but the oldest body I have available is K-30 and not seen any comments thus far that it would be able to do the job.
The other point of interest is screw drive focus speed on the DA* 300. I shoot birds, and a lot of BIF, and am used to the DFA 150-450 on the K-3 II and the K-1, and the focus speed of the SDM may not be up to what I'm used to.
The comments on the speed of the screw drive focus on the DA* 300, relative to the SDM, appear to be a bit variable, so any clarification would be nice.

Cheers,
Terry
02-19-2020, 04:44 AM   #6
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The SDM in my DA* 300 is still OK (I think) so I haven't converted that one, but based on my converted DA* 200 you might find screw-drive with this lens noisier than you'd like for bird photography. Having tried the converted lens on three different camera models, I found that some are noisier than others.

Also, the screw-drive focus usually takes two or three movements to lock in, so I doubt it would be faster at any event.
02-20-2020, 11:26 AM   #7
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My 50-135 needs some times for ''waking-up'' before it can autofocus and I'm thinking about converting it. Is there anyone in montreal with an older pentax camera wich had lens converted ? Since I sold my kx I have no capable camera now :/
02-20-2020, 12:07 PM   #8
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QuoteOriginally posted by tduell Quote
I've been reading this and all the earlier thread with great interest, having just got my hands on a DA* 300 to allow me to get back out with the camera a bit sooner after shoulder surgery, than I would if using the DFA 150-450.
Does anyone here (Australia) provide a service to do the SDM to screw drive conversion?
I would probably have a try at it myself if necessary, but the oldest body I have available is K-30 and not seen any comments thus far that it would be able to do the job.
The other point of interest is screw drive focus speed on the DA* 300. I shoot birds, and a lot of BIF, and am used to the DFA 150-450 on the K-3 II and the K-1, and the focus speed of the SDM may not be up to what I'm used to.
The comments on the speed of the screw drive focus on the DA* 300, relative to the SDM, appear to be a bit variable, so any clarification would be nice.

Cheers,
Terry
Quickshift can help with both SDM and ScrewDrive. I think the K-1 will focus faster due to improved focus overall with the lens in either mode. I would expect you need to find someone to borrow an older body from or purchase an older body from. The K-30 like the K-50 will not work for conversion.

02-20-2020, 12:10 PM   #9
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QuoteOriginally posted by Password1234 Quote
My 50-135 needs some times for ''waking-up'' before it can autofocus and I'm thinking about converting it. Is there anyone in montreal with an older pentax camera wich had lens converted ? Since I sold my kx I have no capable camera now :/
I have done conversions for Canadian members - but the cost in time for the forms and the shipping costs are a bit much. I can do it but you might be able to buy an older camera and use it and resell it easier than dealing with customs and shipping. I do know that if labeled as returned repaired items there is no import duty (rightly so as you are shipping to me to begin with!)
02-21-2020, 07:25 AM   #10
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QuoteOriginally posted by UncleVanya Quote
I have done conversions for Canadian members - but the cost in time for the forms and the shipping costs are a bit much. I can do it but you might be able to buy an older camera and use it and resell it easier than dealing with customs and shipping. I do know that if labeled as returned repaired items there is no import duty (rightly so as you are shipping to me to begin with!)
I thought there will be some duty involved, I'll probably get an older camera just for the switch, thanks for the reply !

About the focusing speed, I quote Dpreview here '', also K-70 has twice faster screw drive AF motor and old fashion AF lences focusing clear twice faster then on many other cameras (just K3, K3ii, K-S.1, K-S2 and KP have the same fast AF motor).''
If people said there was no differences between sdm vs screw-drive on older model, there might be some difference on newer models.
02-24-2020, 11:54 AM   #11
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QuoteOriginally posted by Password1234 Quote
I thought there will be some duty involved, I'll probably get an older camera just for the switch, thanks for the reply !

About the focusing speed, I quote Dpreview here '', also K-70 has twice faster screw drive AF motor and old fashion AF lences focusing clear twice faster then on many other cameras (just K3, K3ii, K-S.1, K-S2 and KP have the same fast AF motor).''
If people said there was no differences between sdm vs screw-drive on older model, there might be some difference on newer models.
on an unrelated, but sort of related topic, not that i'm in Montreal, but I do have a K5 up for sale. I am based around Toronto, so you wont be charged any import fee
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