SDM working or not

tward · 06-13-2015, 03:37 PM

Being new to Pentax I don't feel too stupid for asking this question. How do you know if the SDM is functioning or not?
Thanks

Adam · 06-13-2015, 03:41 PM

Is your lens focusing when you half-press the shutter button?

tward · 06-13-2015, 03:45 PM

Yep sure does

**jatrax** · 06-13-2015, 03:47 PM

Just to state the obvious: SDM is the focusing motor in the lens. And only some lenses have a focusing motor, and only some of those use an SDM motor. So FIRST, make sure you have an SDM lens.

Second, if you do have an SDM lens, make sure that the camera and lens are both set to autofocus mode. Move both switches back and forth to make sure one is not stuck part way.

If you do have an SDM lens and it is not functioning, then the lens will not autofocus. In severe cases it will not auto focus at all. In less severe cases it will AF sometimes and not others, it might chirp or squeak when you try to focus, it might seem sluggish and take longer to start moving, it might not work at first but after repeated tries start working and be fine the rest of the day.

---------- Post added 06-13-15 at 03:49 PM ----------

Originally posted by tward

Yep sure does

See above. But if you have an SDM lens and the AF is working then why do you think you have a problem? Or are you just asking for future reference? What lens it is by the way, then we can tell whether it will ever be a problem.

Na Horuk · 06-13-2015, 03:53 PM

If the AF works normally (smoothly, silently), then SDM is alright. Its just most lenses have their AF driven by the in-camera motor (screwdrive). But not SDM lenses! Those have a little motor inside the lens. This is why it is more silent, but in some cases it can stop working, and then the lens can no longer allow AF (but you can still do some stuff to salvage such a lens a little bit by disabling SDM and turning it into a screw-drive lens, but this requires a bit of "hacking").

Anyway, don't worry about SDM working or not. You can start worrying if your lens doesn't do AF at all. Then SDM might be the problem.
Also, some lenses are not likely to develop SDM problems. And also also, Pentax claims that new lenses are safe from SDM problems.

tward · 06-13-2015, 03:58 PM

I should have stated from the start. I have a 50-135 that I purchased with the knowledge from the seller the SDM was not functional but of course the screw focus was fine. I was just curious how you know it works or not. I have read here and other places that most disable the SDM or if it fails not to worry about it. I was just curious because the lens focus is fine.

**jatrax** · 06-13-2015, 04:01 PM

Originally posted by tward

I should have stated from the start. I have a 50-135 that I purchased with the knowledge from the seller the SDM was not functional but of course the screw focus was fine. I was just curious how you know it works or not. I have read here and other places that most disable the SDM or if it fails not to worry about it. I was just curious because the lens focus is fine.

If the focus is fine then either:
1) The SDM is fine and working properly, or
2) The previous owner disabled the SDM and set the lens to screw drive mode using a firmware hack

There is no way to "not worry about it" if it fails. If the SDM is not working then the auto focus is not working. See my post above for some symptoms.

K57XR · 06-13-2015, 05:13 PM

Originally posted by tward

I should have stated from the start. I have a 50-135 that I purchased with the knowledge from the seller the SDM was not functional but of course the screw focus was fine. I was just curious how you know it works or not. I have read here and other places that most disable the SDM or if it fails not to worry about it. I was just curious because the lens focus is fine.

If it's already been hacked to screw-drive then the only way I can think of testing the SDM is to "re-hack" it back then test it on a modern body (K100D Super and Up). If you don't have the original firmware (LENSEEP.LNS) file from the seller make sure to make a copy of what's on the lens now before modifying it just to be safe.

Na Horuk · 06-14-2015, 08:00 AM

Oh right. Well, if the AF is a loud whirring, then the lens has already been converted to screw drive. If the AF is silent, then SDM is running.
If the previous owner disable the SDM, then it probably did not work. You can get it repaired, but it costs something.I wouldn't bother enabling it just to have to disable it.
To disable it, you need a certain older DSLR. You can search these forum for guide threads

sterretje · 06-14-2015, 08:41 AM

Surprised that nobody asked the question which camera the lens is used with. If OP has a K100D/K110D or older or a K10D with certain firmware versions, SDM will never work as these cameras don't support SDM.

tward · 06-15-2015, 04:21 AM

K5 sorry for not referencing earlier

06-13-2015, 03:37 PM	#1
tward New Member Join Date: May 2015 Posts: 5	SDM working or not Being new to Pentax I don't feel too stupid for asking this question. How do you know if the SDM is functioning or not? Thanks

06-13-2015, 03:41 PM	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,593	Is your lens focusing when you half-press the shutter button? 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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06-13-2015, 03:45 PM	#3
tward New Member Join Date: May 2015 Posts: 5 Original Poster	Yep sure does

06-13-2015, 03:47 PM	#4
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	Just to state the obvious: SDM is the focusing motor in the lens. And only some lenses have a focusing motor, and only some of those use an SDM motor. So FIRST, make sure you have an SDM lens. Second, if you do have an SDM lens, make sure that the camera and lens are both set to autofocus mode. Move both switches back and forth to make sure one is not stuck part way. If you do have an SDM lens and it is not functioning, then the lens will not autofocus. In severe cases it will not auto focus at all. In less severe cases it will AF sometimes and not others, it might chirp or squeak when you try to focus, it might seem sluggish and take longer to start moving, it might not work at first but after repeated tries start working and be fine the rest of the day. ---------- Post added 06-13-15 at 03:49 PM ---------- Originally posted by tward Yep sure does See above. But if you have an SDM lens and the AF is working then why do you think you have a problem? Or are you just asking for future reference? What lens it is by the way, then we can tell whether it will ever be a problem.

06-13-2015, 03:53 PM	#5
Na Horuk Veteran Member Join Date: Feb 2012 Location: Slovenia, probably Photos: Gallery \| Albums Posts: 11,186	If the AF works normally (smoothly, silently), then SDM is alright. Its just most lenses have their AF driven by the in-camera motor (screwdrive). But not SDM lenses! Those have a little motor inside the lens. This is why it is more silent, but in some cases it can stop working, and then the lens can no longer allow AF (but you can still do some stuff to salvage such a lens a little bit by disabling SDM and turning it into a screw-drive lens, but this requires a bit of "hacking"). Anyway, don't worry about SDM working or not. You can start worrying if your lens doesn't do AF at all. Then SDM might be the problem. Also, some lenses are not likely to develop SDM problems. And also also, Pentax claims that new lenses are safe from SDM problems.

06-13-2015, 03:58 PM	#6
tward New Member Join Date: May 2015 Posts: 5 Original Poster	I should have stated from the start. I have a 50-135 that I purchased with the knowledge from the seller the SDM was not functional but of course the screw focus was fine. I was just curious how you know it works or not. I have read here and other places that most disable the SDM or if it fails not to worry about it. I was just curious because the lens focus is fine.

06-13-2015, 04:01 PM	#7
jatrax Site Supporter Join Date: May 2010 Location: Washington Cascades Photos: Gallery \| Albums Posts: 12,991	Originally posted by tward I should have stated from the start. I have a 50-135 that I purchased with the knowledge from the seller the SDM was not functional but of course the screw focus was fine. I was just curious how you know it works or not. I have read here and other places that most disable the SDM or if it fails not to worry about it. I was just curious because the lens focus is fine. If the focus is fine then either: 1) The SDM is fine and working properly, or 2) The previous owner disabled the SDM and set the lens to screw drive mode using a firmware hack There is no way to "not worry about it" if it fails. If the SDM is not working then the auto focus is not working. See my post above for some symptoms.

06-13-2015, 05:13 PM	#8
K57XR Veteran Member Join Date: Feb 2011 Location: Colorado, USA Posts: 830	Originally posted by tward I should have stated from the start. I have a 50-135 that I purchased with the knowledge from the seller the SDM was not functional but of course the screw focus was fine. I was just curious how you know it works or not. I have read here and other places that most disable the SDM or if it fails not to worry about it. I was just curious because the lens focus is fine. If it's already been hacked to screw-drive then the only way I can think of testing the SDM is to "re-hack" it back then test it on a modern body (K100D Super and Up). If you don't have the original firmware (LENSEEP.LNS) file from the seller make sure to make a copy of what's on the lens now before modifying it just to be safe.

06-14-2015, 08:00 AM	#9
Na Horuk Veteran Member Join Date: Feb 2012 Location: Slovenia, probably Photos: Gallery \| Albums Posts: 11,186	Oh right. Well, if the AF is a loud whirring, then the lens has already been converted to screw drive. If the AF is silent, then SDM is running. If the previous owner disable the SDM, then it probably did not work. You can get it repaired, but it costs something.I wouldn't bother enabling it just to have to disable it. To disable it, you need a certain older DSLR. You can search these forum for guide threads

06-14-2015, 08:41 AM	#10
sterretje Veteran Member Join Date: Dec 2008 Location: Roodepoort, South Africa Photos: Gallery \| Albums Posts: 3,561	Surprised that nobody asked the question which camera the lens is used with. If OP has a K100D/K110D or older or a K10D with certain firmware versions, SDM will never work as these cameras don't support SDM.

06-15-2015, 04:21 AM	#11
tward New Member Join Date: May 2015 Posts: 5 Original Poster	K5 sorry for not referencing earlier

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