How to "de-SDM" a lens or teleconvertor?

Gengh · 25th April 2009

I've got the Kenko Pz-AF 1.5x Teleplus MC, and if I'm not wrong this model has the "SDM-like" leads/contacts, but they were actually meant for the power zooms in old lenses. When I use it with the K20D and the DA* lenses, the SDM motor works, but the combi cannot get a focus lock. I think the teleconvertor causes the AF to over-compensate somehow, and always overshoots when trying to focus.

I've tried taping the SDM contacts up with a sticker on the teleconvertor, and I thought that will make the body think that there's a non-SDM lens attached to it so it'll just AF with the screw drive motor. But that didn't work, the AF doesn't work at all, and the K20D seem to be telling me to switch to MF mode (the "MF" indicator keeps flashing in the viewfinder). Then I tried taping up the SDM contacts on the DA*16-50 instead, and the same thing happens, both with and without the teleconvertor.

I thought blocking the SDM contacts was enough to "de-SDM" a lens to make it go back to the screw drive AF motor, seems like I'm wrong. Is there another one of the contact pins that I need to block? Anyone knows?

LancerEX · 25th April 2009

hi gengh, i was reading up on the pentaxforums about teleconverters too for many nights. check out @http://www.pentaxforums.com/forums/pentax-slr-lens-discussion/38514-converting-kenko-2x-converter-sdm.html

it seems that kenko teleplus may have some issues with SDM ... i am looking for a tamron 1.4x MC4 instead to work with DA* lenses, play safe a bit.

Gengh · 25th April 2009

Oh yah, I already knew that this teleconvertor is not SDM-friedly, you need the SHQ version, which mine is not. That's why I wanted to just block out the SDM and get the K20D to use the screw drive AF. The AF worked like a gem with the K100D even with slow lenses like the Tamron 70-300mm, so if I can get the K20D to fall back on the screw drive AF I'm sure it'll be ok.

Just don't feel like hunting around for another teleconvertor unless I really have to....

scurrvy · 30th April 2009

I'd like to know how to do this too, as my 16-50 won't focus with the SDM on my k20d, but the screw drive works fine with the k100d. I've googled extensively and haven't found anything. I wish there was an option to disable sdm in the menus.

felixcat8888 · 30th April 2009

Originally Posted by scurrvy

I'd like to know how to do this too, as my 16-50 won't focus with the SDM on my k20d, but the screw drive works fine with the k100d. I've googled extensively and haven't found anything. I wish there was an option to disable sdm in the menus.

What is your firmware version? The 16-50 should focus with no issues on the K20D.

fengwei · 30th April 2009

Originally Posted by felixcat8888

What is your firmware version? The 16-50 should focus with no issues on the K20D.

If the SDM is damaged, it won't AF on a camera like K10D/K20D/K100Ds/K200. But it'd AF fine on pre-SDM cameras.

Gengh · 30th April 2009

Originally Posted by scurrvy

I'd like to know how to do this too, as my 16-50 won't focus with the SDM on my k20d, but the screw drive works fine with the k100d. I've googled extensively and haven't found anything. I wish there was an option to disable sdm in the menus.

I remember reading somwhere on pentaxforums that the K20D doesn't have the option to disable SDM in the menus (was available in K10D).

But it's very strange that the 16-50 won't focus with SDM, hate to say this but maybe your SDM motor needs repair. This problem happened with a batch of 50-135, maybe it affects 16-50 too.

felixcat8888 · 30th April 2009

Looks like scurrvy needs to send lens in for diagnosis.

skypacker · 30th April 2009

Originally Posted by scurrvy

I'd like to know how to do this too, as my 16-50 won't focus with the SDM on my k20d, but the screw drive works fine with the k100d. I've googled extensively and haven't found anything. I wish there was an option to disable sdm in the menus.

Most likely an SDM failure. It happened to my 50-135 and I believe Gengh's too; we had the SDM replaced by Pentax Japan under warranty. In my case, it focused perfectly with the screw-drive on a K100D, but would not lock focus on the K20D.

If one is to go by DPreview reports, then the 16-50 also has the same problem. The * primes seem to be immune from SDM failures so far.

Send it in for service.

flowerpot · 30th April 2009

maybe there will be a new firmware to de-SDM a lens...should not be too difficult... i like the word de-SDM...hehe

hopefully there is a de-underexpose and de-slow low light AF as well

scurrvy · 30th April 2009

Well, I just purchased the lens from Camera Workshop in Peninsular Shopping Center. Probably not the best place to buy a lens. When I tested it in the store, it locked focus, but I didn't realize till later that all of my test shots were at infinity. (doh!) I'm going to try to return the lens today, but I'm not very hopefully they'll let me. Has anyone bought from this place before? I also bought a 50-135 from this place and it's working fine so far. They're asking $1050 for the 50-135, I got it for $980 cash. They have two more 50-135... they both seemed okay to me... If anyone else is looking.

felixcat8888 · 30th April 2009

Originally Posted by scurrvy

Well, I just purchased the lens from Camera Workshop in Peninsular Shopping Center. Probably not the best place to buy a lens. When I tested it in the store, it locked focus, but I didn't realize till later that all of my test shots were at infinity. (doh!) I'm going to try to return the lens today, but I'm not very hopefully they'll let me. Has anyone bought from this place before? I also bought a 50-135 from this place and it's working fine so far. They're asking $1050 for the 50-135, I got it for $980 cash. They have two more 50-135... they both seemed okay to me... If anyone else is looking.

16-50 and 50-135 are grey sets from TCW. You can go back and get them to replace it for you but they may or may not as the lens do not come with the original boxes.
Last time I enquired, no mention of shop warranty only that they are helping someone get rid of stock as that someone shop has closed down . . .
Please do homework first before buying. No box = 100% grey. dubious origin also . . .

flowerpot · 30th April 2009

Originally Posted by scurrvy

Well, I just purchased the lens from Camera Workshop in Peninsular Shopping Center. Probably not the best place to buy a lens. When I tested it in the store, it locked focus, but I didn't realize till later that all of my test shots were at infinity. (doh!) I'm going to try to return the lens today, but I'm not very hopefully they'll let me. Has anyone bought from this place before? I also bought a 50-135 from this place and it's working fine so far. They're asking $1050 for the 50-135, I got it for $980 cash. They have two more 50-135... they both seemed okay to me... If anyone else is looking.

did they say got shop warranty... if yes AFAIK they do honor it... u must have bought it very recently cos i saw 3 just last weekend...perhaps can do a swap with either 2 there.

scurrvy · 1st May 2009

They gave me a full refund. So if you see a 16-50 at TCW, check out the focus. It would lock at infinity, but not anywhere else.

25th April 2009	#1
Gengh Contributor Join Date: May 2007 Location: Florida Posts: 1,163	How to "de-SDM" a lens or teleconvertor? I've got the Kenko Pz-AF 1.5x Teleplus MC, and if I'm not wrong this model has the "SDM-like" leads/contacts, but they were actually meant for the power zooms in old lenses. When I use it with the K20D and the DA* lenses, the SDM motor works, but the combi cannot get a focus lock. I think the teleconvertor causes the AF to over-compensate somehow, and always overshoots when trying to focus. I've tried taping the SDM contacts up with a sticker on the teleconvertor, and I thought that will make the body think that there's a non-SDM lens attached to it so it'll just AF with the screw drive motor. But that didn't work, the AF doesn't work at all, and the K20D seem to be telling me to switch to MF mode (the "MF" indicator keeps flashing in the viewfinder). Then I tried taping up the SDM contacts on the DA*16-50 instead, and the same thing happens, both with and without the teleconvertor. I thought blocking the SDM contacts was enough to "de-SDM" a lens to make it go back to the screw drive AF motor, seems like I'm wrong. Is there another one of the contact pins that I need to block? Anyone knows?

25th April 2009	#2
LancerEX Member Join Date: Feb 2008 Posts: 386	Re: How to "de-SDM" a lens or teleconvertor? hi gengh, i was reading up on the pentaxforums about teleconverters too for many nights. check out @http://www.pentaxforums.com/forums/pentax-slr-lens-discussion/38514-converting-kenko-2x-converter-sdm.html it seems that kenko teleplus may have some issues with SDM ... i am looking for a tamron 1.4x MC4 instead to work with DA* lenses, play safe a bit.

25th April 2009	#3
Gengh Contributor Join Date: May 2007 Location: Florida Posts: 1,163	Re: How to "de-SDM" a lens or teleconvertor? Oh yah, I already knew that this teleconvertor is not SDM-friedly, you need the SHQ version, which mine is not. That's why I wanted to just block out the SDM and get the K20D to use the screw drive AF. The AF worked like a gem with the K100D even with slow lenses like the Tamron 70-300mm, so if I can get the K20D to fall back on the screw drive AF I'm sure it'll be ok. Just don't feel like hunting around for another teleconvertor unless I really have to....

30th April 2009	#4
scurrvy New Member Join Date: Apr 2009 Posts: 17	Re: How to "de-SDM" a lens or teleconvertor? I'd like to know how to do this too, as my 16-50 won't focus with the SDM on my k20d, but the screw drive works fine with the k100d. I've googled extensively and haven't found anything. I wish there was an option to disable sdm in the menus.

30th April 2009	#8
felixcat8888 Senior Member Join Date: May 2005 Location: Delta Posts: 3,675	Re: How to "de-SDM" a lens or teleconvertor? Looks like scurrvy needs to send lens in for diagnosis. __________________ Ricoh XR-P,Chinon CP-7m,Pentax Z-1SE/MZ-S/K20D+16-50mm F2.8+FA43mm F1.9 Limited,Metz 58 AF-1P

30th April 2009	#10
flowerpot Member Join Date: Mar 2007 Location: Both East n West Posts: 2,242	Re: How to "de-SDM" a lens or teleconvertor? maybe there will be a new firmware to de-SDM a lens...should not be too difficult... i like the word de-SDM...hehe hopefully there is a de-underexpose and de-slow low light AF as well __________________ ~Towards Sublime Gallery~

1st May 2009	#14
scurrvy New Member Join Date: Apr 2009 Posts: 17	Re: How to "de-SDM" a lens or teleconvertor? They gave me a full refund. So if you see a 16-50 at TCW, check out the focus. It would lock at infinity, but not anywhere else.