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07-27-2020, 07:38 AM - 1 Like   #16
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While I am known for converting a lot of this site's members' lenses, I only own one converted lens myself, a da* 16-50. My other conversion capable lenses have been converted back and forth a couple of times but continue to work reliably in sdm.

The 16-50 is louder than it would be but not objectionably. The DA* all weather design seems to make some of the noise. I personally don't find the screw drive noise bothersome.

I encourage anyone with a broken sdm DA* lens capable of conversion (16-50, 50-135, 200 & 300) with the necessary camera body and knowledge to try it before laying down the money for sdm refurbishment.

But if you have tried it and found it isn't what you want, then sdm replacement is a good idea.

07-27-2020, 09:06 AM   #17
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Unfortunately two SDM versions; DA 17-70 and DA* 55 are SDM only and cannot be converted. I will bite the bullet and send my 17-70 to either Precision or KEH and get the motor replaced. Hopefully the new motor will be a more durable design than the old one. Had it been convertible to screw drive I definitely would have gone that route.
07-27-2020, 10:17 AM   #18
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I have both a DA 16-45 and a DA*16-50 that it is replacing due to a bit too much wobble on the 16-45 causing optical issues.
The DA*16-50 has been converted to screwdrive due to a dead SDM motor.
I have to say that the DA*16-50 screw drive, while probably not louder than the 16-45, feels louder because it always takes twice the time to focus. While the 16-45 is always decisive in focusing, the 16-50 is always fine-tuning the focus before locking on a subject. So the noise is twice as long... I'm not sure the SDM focusing also takes a bit longer than other lenses as it goes back and forth?
I'm not going to get the DA*16-50 repaired as to me it is not worth the cost, especially if it's not going to focus faster. I do wish it would focus as fast as my DA 16-45 or the DA 35 "Plastic Fantastic"... but I'm learning to live with it because at least the focusing seems pretty reliable once it does lock focus, and the metering is also always spot on - no constant underexposing like the DA 16-45 is so fond of doing... most importantly, I am very pleased with the images I'm getting from it .
07-27-2020, 11:46 AM   #19
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I have one of the first 16-50 lenses which failed shortly after the warrantee ran out. I had a K10D at the time and had updated the firmware for the body to recognise SDM. Before the update, the lens worked by screw drive, but afterwards it was SDM or nothing. I saw some videos of the lens strip down and followed the instructions. The motor has a JIS crosspoint screw in the end (similar to Phillips) and you had to use a screwdriver to turn the motor shaft clockwise and anticlockwise a few times before re assembling the lens. The SDM worked for a time before jamming once more. I took the lens apart again and before re assembling it, I drilled a hole in the rear mount in line with the motor screw. This was inboard of the sealing ring, so didn't affect the waterproofing. The screwdriver could be used to free up the motor without taking the lens apart. The strange thing was that ever since, the SDM has worked without resorting to using the screwdriver. I don't use the lens much, but always point the camera at a plain wall and using the AF button make the lens focus hunt from end to end a few times. It takes exactly 2 seconds to cycle fully.

07-27-2020, 01:11 PM   #20
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QuoteOriginally posted by jddwoods Quote
Unfortunately two SDM versions; DA 17-70 and DA* 55 are SDM only and cannot be converted. I will bite the bullet and send my 17-70 to either Precision or KEH and get the motor replaced. Hopefully the new motor will be a more durable design than the old one. Had it been convertible to screw drive I definitely would have gone that route.
The DA* 60-250mm f/4 is another lens where, unfortunately, screw-drien conversion is not possible. At least with the conversion available for the DA* 16-50mm, one then has a full-function lens. And there are many reports of the screw-driven version having faster AF, but maybe not with the DA* 16-50mm. My FA* 300mm f/4.5 has only screw-driven AF but its AF is very fast and sure on my KP. In fact, the AF of other screw-driven lenses I have, even the DA 55-300mm f/4-5.8 WR, have shown decidedly improved performance with this camera! Therefore, one advantage of the old screw-driven technology, in addition to reliability, is the possibility of upgraded performance via a new camera model! The premium Pentax Limited primes continue to be screw-driven.

I've seen many instances come up on this forum, including this thread, where the SDM was replaced only to fail again. The SDM issue, in addition to cost, was my reason for choosing the Sigma 17-50mm f/2.8 EX DC HSM instead. No WR, but I am very pleased with it in every other way.

Pentax has since switched to DC motors, which have proven to be reliable, or in some cases a new SDM motor design. So it mystifies me that there was no upgrade of motors in these older lens models, replacing the old failure-prone designs. The highly-regarded DA* 60-250mm f/4 especially beckons for such an upgrade, with its very fine performance capability, and also its adaptability for FF use. Developing a whole new DFA 70-200mm f/4 with a reduced zoom range instead of upgrading the AF motor in this fine lens was a decision that is beyond my comprehension.

Last edited by mikesbike; 07-27-2020 at 01:23 PM.
07-27-2020, 05:40 PM   #21
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For those who may be wondering, after getting my K1 II I sold both converted DA* lenses - the 16-50 and 50-135 - at normal market prices. I seems that people are happy with the screw drive over the SDM which, in my opinion, is not a big deal and pushes the price new up too much... The new full frame D FA SDMs are much better.
07-27-2020, 07:42 PM   #22
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I converted my almost new FA 16-50 to screw drive, and love it. No more SDM worries, and focusing is great. If you have one of these, go ahead and convert it and then you can forget it ever failing.

07-27-2020, 08:08 PM   #23
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QuoteOriginally posted by stevebrot Quote
It really is not needed. Screw drive only cameras (e.g. K100D, *ist D) work fine with the your lens. Those that support motor-in-lens work fine too, assuming the motor is working. I don't understand the frustration and push-back. If you purchased the inoperable lens with the assumption that parts would be readily available for a cheap fix, that was an unfortunate choice. Very few (no?) camera companies sell parts direct to consumers anymore and very few authorized repair shops sell parts as a pass-through. Sometimes U.S. Camera has Pentax parts, but not for your lens; I just checked. KEH may be able to repair your lens, but their pricing is flat rate and would be similar to Precision. The story is similar for Advance Camera in Portland.

If it were me, motor replacement would never have been on the table, knowing that the screwdrive conversion is so highly regarded by owners on this site. I have never read a complaint from anyone that has done it, just gratitude that someone figured out how it might be done. It is a very clever hack, IMHO.

Good luck. I hope you are able to get a satisfactory working lens without a lot of additional expense.

Edit: In regards to simply making screwdrive switchable, the capability actually is not there, natively. The "fix" involves rewriting the EPROM in the lens using a screw-drive-only body running in debug mode to do the write.


Steve
Well the lens was purchased probably 6-8 years ago used through Borrowlenses via their used lens program for around 350US if I recall. So perhaps "cheap" isn't exactly the most ideal way of putting it. When I received the "Working" lens from BL the SDM would work about 3/4 of the time. I Requested a different lens from BL and they obliged. Fast forward to the difficulties of life that led me to lay this particular brand biome down for a few years and now I've picked it back up with an SDM lens that is completely nonfunctional.

As far as making screwdrive switchable, and not being native... well obviously it's not. I'm saying I see no reason it couldn't be though. Considering the "Fix" I see no reason why Pentax could not write a program within the settings menu to change the camera capabilities to "Screw drive only". As these lenses work with screw drive only bodies, this could theoretically be an option within the camera to make the lens think the camera only has screw drive capability.

Thanks for your input...
07-27-2020, 08:20 PM   #24
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QuoteOriginally posted by Dtabbler Quote
Thanks for your input...
Thanks for checking in with us. It has been awhile. Sorry we could not provide the answer you needed to hear.


Steve
07-28-2020, 01:27 AM   #25
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]INPIRED BY UNCLE VANYA
I know that my ears are not what they have been, but the noise from the screw drive af is for me a little sound.
A few times I have been a wedding photographer with K 30 ,and KP. The af sound could not compete with the wind in the branches and above all: noisy aunts and girlfreinds So relax

Last edited by niels hansen; 07-28-2020 at 01:32 AM. Reason: bad editing
07-28-2020, 07:35 PM - 1 Like   #26
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Sdm and screw drive focusing behavior isn't exactly the same even on converted lenses. The sdm when fresh and working well has a fine tuning behavior that seems to take a bit to settle in in hard to focus situations. In similar situations screwdrive has coarser movements and jumps back and forth shooting past focus more than sdm. But when sdm is failing it gives up before screwdrive and stops trying when the focusing is difficult. This is observed behavior in actual lenses on the same body. Neither is particularly fast or slow but failing sdm can be quite a bit slower.
07-29-2020, 09:19 AM   #27
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QuoteOriginally posted by UncleVanya Quote
Sdm and screw drive focusing behavior isn't exactly the same even on converted lenses. The sdm when fresh and working well has a fine tuning behavior that seems to take a bit to settle in in hard to focus situations. In similar situations screwdrive has coarser movements and jumps back and forth shooting past focus more than sdm. But when sdm is failing it gives up before screwdrive and stops trying when the focusing is difficult. This is observed behavior in actual lenses on the same body. Neither is particularly fast or slow but failing sdm can be quite a bit slower.
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
07-29-2020, 11:06 AM   #28
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QuoteOriginally posted by stevebrot Quote
Precision in Connecticut is the authorized repair facility and presumably can get parts. Conventional wisdom is that while repair is possible, the permanence of repair may not be, hence the recommendation to convert to screw drive. Since you got the lens for cheap, why pour money into what might be an expensive ($500+ ??) repair?
You can get quotes from the Precision page:Ricoh Imaging Americas Corporation - Service & Repair

Running through a couple SDM lenses, the 16-50 was quoted at $242, and the 55mm was $302.50. For comparison, I got a 16-50 fixed in 2012 from C.R.I.S., when they were the official Pentax repair, and it was $216.
07-29-2020, 12:15 PM   #29
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QuoteOriginally posted by leekil Quote
You can get quotes from the Precision page:Ricoh Imaging Americas Corporation - Service & Repair

Running through a couple SDM lenses, the 16-50 was quoted at $242, and the 55mm was $302.50. For comparison, I got a 16-50 fixed in 2012 from C.R.I.S., when they were the official Pentax repair, and it was $216.
Thanks! If Precision will do the repair (flat rate, parts included) for $242, that is a pretty good deal.


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07-29-2020, 08:43 PM   #30
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I think the price quoted by Precision is "typical" but I've never been clear it's flat rate. I know some lenses even ones still sold at the time of repair were returned as economically infeasible to repair. Those needed more than a simple sdm repair however.
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