SDM Auto focus

n7wdit · 05-25-2017, 11:04 AM

I just bought the DA* 60 - 250 F4 Lens. I have read several reviews of the lens. This is my first SDM auto Focus lens. My question is the SDM system dependable. Do I need to do anything special to keep the lens working correctly? I have two K3's. I do some landscape work and enjoy doing bird watching.

I have the posts on the forum for some time. I normally enjoy reading the dedicated Pentax info.

Adam · 05-25-2017, 11:18 AM

Originally posted by n7wdit

I just bought the DA* 60 - 250 F4 Lens. I have read several reviews of the lens. This is my first SDM auto Focus lens. My question is the SDM system dependable. Do I need to do anything special to keep the lens working correctly? I have two K3's. I do some landscape work and enjoy doing bird watching.

I have the posts on the forum for some time. I normally enjoy reading the dedicated Pentax info.

The early SDM system such as that used in this lens is known to have some reliability issues. A hardware design flaw in the SDM was addressed a few years ago, so all new 60-250mm should be more dependable. However, user reports seem to recommend that you should regularly use the lens (i.e. at least once a week) if you want to keep the SDM from failing in the long term.

Other in-lens focusing systems such as DC, PLM, or even Tamron's "SDM" in the 24-70mm, 15-30mm, and 18-270mm is very dependable and at least as reliable as screwdrive.

**clickclick** · 05-25-2017, 11:59 AM

Originally posted by Adam

[snip] However, user reports seem to recommend that you should regularly use the lens (i.e. at least once a week) if you want to keep the SDM from failing in the long term.
[snip]

Any idea why the once a week use? Makes it almost sound like a lubrication issue and keeping grease distributed so it doesn't collect in low spots when sitting. It is a great excuse to have to use the lenses though! Time to do more with my 50-135

.

Adam · 05-25-2017, 12:01 PM

I think that's exactly the problem. Too much strain on the motor and it otherwise breaks down.

Adam
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**UncleVanya** · 05-25-2017, 03:51 PM - **2 Likes**

Originally posted by clickclick

Any idea why the once a week use? Makes it almost sound like a lubrication issue and keeping grease distributed so it doesn't collect in low spots when sitting. It is a great excuse to have to use the lenses though! Time to do more with my 50-135

.

I honestly think the 1/week thing is magical thinking. They do it and think it helps. I don't do it. And mine work just fine also (DA* 200, DA* 16-50, DA* 50-135, DA* 60-250). Additionally it makes little sense. The lenses sit in boxes sometimes for years and work fine and then somehow need extra exercise weekly? I'm not buying it. But that's the prevailing wisdom. Take it with a grain of salt.

My crackpot theory is that something in the lens is bad - a bent or out of compliance part and it adds drag and slowly hurts the motor by demanding too much from it. Replace the motor - same lens - may have the same problem because the underlying problem is still there. And in the interests of reversing myself from above - if the part is bound up adding additional torque it might get worse over time if unused and some tiny adhesion formed. Personally I still don't see it, but people swear by it. Your mileage may vary. Good units just tend to work and stay working - at least that's my own magical thinking. To put your mind at east, the 60-250 is one of the least reported lenses for failures; so I would not worry too much.

**clickclick** · 05-25-2017, 04:09 PM

I'm thinking if it really is tied into keeping mechanisms evenly lubed for whatever reason, you could "warm up" a lens by cycling the focus, and if applicable, zoom it 10 times or some other ritualistic amount that would really probably exceed the range of travel in typical use. This sounds like a situation where a doll and pins might even help

gm4life · 05-25-2017, 05:51 PM

I say enjoy it, that is a great lens. The motors the last few years (since like 2014 or something) have been improved/revised from what I can tell. I do get my two SDM's DA 55 and DA 300 out at least twice a month and so far am loving them as they are super silent.

The 60-250 or maybe the FF 70-200 is on my bucket list. Likely will sit tight and wait for my DFA 85 and sit tight.

JohnX · 05-25-2017, 11:45 PM

The idea of running the lens weekly seems to help, either due to overcoming 'stiction' in the gearing or reviving drained capacitors in the circuitry, the latter idea stemming from experience here in the UK. Attach the lens, and if it doesn't work immediately, simply leave it with the camera switched on for a few minutes and invariably it will then focus without any further fuss.

Kunzite · 05-26-2017, 02:15 AM - **1 Like**

I'd often leave my 60-250 unused for long-ish periods; its SDM didn't give me any issues. YMMV.

The "reviving drained capacitors" is utter nonsense; and I know who's guilty of that. If you think you're experienced it, you're wrong.

jddwoods · 05-26-2017, 03:24 AM

we can debate or debunk these theories of why SDM motors need to be "exercised" periodically, but one thing is clear to me. My experience with my two SDM lenses: DA 17-70 and DA* 200 are that if I do not use them on a regular basis, the SDM on both will hesitate to work for a while, depending on how long they were unused. For the DA 17-70, it needs to be used at least once every week, the DA* can sit for about 2 months but longer and it will also hesitate. I have no DC lenses so I do not know if they behave the same but my 55-300 PLM does not behave this way. Once it is mounted on the camera it is instantly ready.

Kunzite · 06-04-2017, 01:42 AM

A possible explanation is stiction.

Rnovo · 06-04-2017, 05:54 PM

Well said Uncle Vania, I just read this thread and rushed over to try my 16-50mm (2008) and 50-135mm (2012) and guess what... none of their SDMs work, either on my K5 or K5IIs. My 10-17mm fisheye and 18-55WR work flawlessly on both cameras.

Granted, I haven't used 50-135 for a while but I did use my 16-50 2 weeks ago. I tried them, turned the focus wheel, turn the camera off and on, used the AF button and the half press numerous time... no deal! I'm fed up with those SDMs, more so since I had a big argument with Sun Camera of Toronto with the 16-50mm fixed as "under warranty", not mentioning the hassles before. Working the SDM every week is lot of bull...for Pentax products!

All worked well for a couple of years but now I'm convinced that the SDM system is a piece of s...t and i've decided to look seriously into switching to screw drive.

That's my 2 cents on this subject...!

**UncleVanya** · 06-04-2017, 08:50 PM

I have converted a lot of lenses. People always seem very happy with them.

05-25-2017, 11:04 AM	#1
n7wdit New Member Join Date: Jan 2016 Posts: 2	SDM Auto focus I just bought the DA* 60 - 250 F4 Lens. I have read several reviews of the lens. This is my first SDM auto Focus lens. My question is the SDM system dependable. Do I need to do anything special to keep the lens working correctly? I have two K3's. I do some landscape work and enjoy doing bird watching. I have the posts on the forum for some time. I normally enjoy reading the dedicated Pentax info.

05-25-2017, 11:18 AM	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,608	Originally posted by n7wdit I just bought the DA* 60 - 250 F4 Lens. I have read several reviews of the lens. This is my first SDM auto Focus lens. My question is the SDM system dependable. Do I need to do anything special to keep the lens working correctly? I have two K3's. I do some landscape work and enjoy doing bird watching. I have the posts on the forum for some time. I normally enjoy reading the dedicated Pentax info. The early SDM system such as that used in this lens is known to have some reliability issues. A hardware design flaw in the SDM was addressed a few years ago, so all new 60-250mm should be more dependable. However, user reports seem to recommend that you should regularly use the lens (i.e. at least once a week) if you want to keep the SDM from failing in the long term. Other in-lens focusing systems such as DC, PLM, or even Tamron's "SDM" in the 24-70mm, 15-30mm, and 18-270mm is very dependable and at least as reliable as screwdrive. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

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05-25-2017, 11:59 AM	#3
clickclick Loyal Site Supporter Join Date: May 2016 Location: East Coast Posts: 2,903	Originally posted by Adam [snip] However, user reports seem to recommend that you should regularly use the lens (i.e. at least once a week) if you want to keep the SDM from failing in the long term. [snip] Any idea why the once a week use? Makes it almost sound like a lubrication issue and keeping grease distributed so it doesn't collect in low spots when sitting. It is a great excuse to have to use the lenses though! Time to do more with my 50-135 .

05-25-2017, 12:01 PM	#4
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,608	I think that's exactly the problem. Too much strain on the motor and it otherwise breaks down. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

05-25-2017, 03:51 PM - 2 Likes	#5
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,454	Originally posted by clickclick Any idea why the once a week use? Makes it almost sound like a lubrication issue and keeping grease distributed so it doesn't collect in low spots when sitting. It is a great excuse to have to use the lenses though! Time to do more with my 50-135 . I honestly think the 1/week thing is magical thinking. They do it and think it helps. I don't do it. And mine work just fine also (DA* 200, DA* 16-50, DA* 50-135, DA* 60-250). Additionally it makes little sense. The lenses sit in boxes sometimes for years and work fine and then somehow need extra exercise weekly? I'm not buying it. But that's the prevailing wisdom. Take it with a grain of salt. My crackpot theory is that something in the lens is bad - a bent or out of compliance part and it adds drag and slowly hurts the motor by demanding too much from it. Replace the motor - same lens - may have the same problem because the underlying problem is still there. And in the interests of reversing myself from above - if the part is bound up adding additional torque it might get worse over time if unused and some tiny adhesion formed. Personally I still don't see it, but people swear by it. Your mileage may vary. Good units just tend to work and stay working - at least that's my own magical thinking. To put your mind at east, the 60-250 is one of the least reported lenses for failures; so I would not worry too much.

05-25-2017, 04:09 PM	#6
clickclick Loyal Site Supporter Join Date: May 2016 Location: East Coast Posts: 2,903	I'm thinking if it really is tied into keeping mechanisms evenly lubed for whatever reason, you could "warm up" a lens by cycling the focus, and if applicable, zoom it 10 times or some other ritualistic amount that would really probably exceed the range of travel in typical use. This sounds like a situation where a doll and pins might even help

05-25-2017, 05:51 PM	#7
gm4life Veteran Member Join Date: Dec 2016 Posts: 602	I say enjoy it, that is a great lens. The motors the last few years (since like 2014 or something) have been improved/revised from what I can tell. I do get my two SDM's DA 55 and DA 300 out at least twice a month and so far am loving them as they are super silent. The 60-250 or maybe the FF 70-200 is on my bucket list. Likely will sit tight and wait for my DFA 85 and sit tight.

05-25-2017, 11:45 PM	#8
JohnX Pentaxian Join Date: Jul 2009 Location: London Posts: 1,116	The idea of running the lens weekly seems to help, either due to overcoming 'stiction' in the gearing or reviving drained capacitors in the circuitry, the latter idea stemming from experience here in the UK. Attach the lens, and if it doesn't work immediately, simply leave it with the camera switched on for a few minutes and invariably it will then focus without any further fuss.

05-26-2017, 02:15 AM - 1 Like	#9
Kunzite Pentaxian Join Date: Apr 2007 Location: Romania Posts: 15,132	I'd often leave my 60-250 unused for long-ish periods; its SDM didn't give me any issues. YMMV. The "reviving drained capacitors" is utter nonsense; and I know who's guilty of that. If you think you're experienced it, you're wrong.

05-26-2017, 03:24 AM	#10
jddwoods Pentaxian Join Date: Nov 2012 Location: Newark, Delaware Posts: 1,035	we can debate or debunk these theories of why SDM motors need to be "exercised" periodically, but one thing is clear to me. My experience with my two SDM lenses: DA 17-70 and DA* 200 are that if I do not use them on a regular basis, the SDM on both will hesitate to work for a while, depending on how long they were unused. For the DA 17-70, it needs to be used at least once every week, the DA* can sit for about 2 months but longer and it will also hesitate. I have no DC lenses so I do not know if they behave the same but my 55-300 PLM does not behave this way. Once it is mounted on the camera it is instantly ready.

06-04-2017, 01:42 AM	#11
Kunzite Pentaxian Join Date: Apr 2007 Location: Romania Posts: 15,132	A possible explanation is stiction.

06-04-2017, 05:54 PM	#12
Rnovo Closed Account Join Date: Mar 2008 Location: Halifax, Nova Scotia, Canada Photos: Gallery \| Albums Posts: 415	Well said Uncle Vania, I just read this thread and rushed over to try my 16-50mm (2008) and 50-135mm (2012) and guess what... none of their SDMs work, either on my K5 or K5IIs. My 10-17mm fisheye and 18-55WR work flawlessly on both cameras. Granted, I haven't used 50-135 for a while but I did use my 16-50 2 weeks ago. I tried them, turned the focus wheel, turn the camera off and on, used the AF button and the half press numerous time... no deal! I'm fed up with those SDMs, more so since I had a big argument with Sun Camera of Toronto with the 16-50mm fixed as "under warranty", not mentioning the hassles before. Working the SDM every week is lot of bull...for Pentax products! All worked well for a couple of years but now I'm convinced that the SDM system is a piece of s...t and i've decided to look seriously into switching to screw drive. That's my 2 cents on this subject...!

06-04-2017, 08:50 PM	#13
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,454	I have converted a lot of lenses. People always seem very happy with them.