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05-28-2009, 03:29 PM   #1
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How to cover the SDM contact pin?

Hi guys,

does anybody know what to use to cover the contact pin on a TeleConverter Lens?

I'm thinking to cover the SDM / Power Zoom contact on my Tamron 1.4x TC (or the ones on the DA* lens) and see how it will work with my DA*16-50 / 50-135.
If I can cover that pin, I assume the lens will work with the old AF motor just like a regular lens.

Is it safe to do?
Most important is what is the best way to block this pin.

Thanks,

05-28-2009, 03:47 PM   #2
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Have you tried a piece of electrical tape?

Do it in the TC, the side that the lens is attached to. This is to prevent the piece of tape from being detached and falling into the camera body.
05-28-2009, 04:18 PM   #3
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QuoteOriginally posted by HermanLee Quote
If I can cover that pin, I assume the lens will work with the old AF motor just like a regular lens.
Is that really a plausible assumption?
05-28-2009, 04:22 PM   #4
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QuoteOriginally posted by HermanLee Quote
Hi guys,

does anybody know what to use to cover the contact pin on a TeleConverter Lens?

I'm thinking to cover the SDM / Power Zoom contact on my Tamron 1.4x TC (or the ones on the DA* lens) and see how it will work with my DA*16-50 / 50-135.
If I can cover that pin, I assume the lens will work with the old AF motor just like a regular lens.

Is it safe to do?
Most important is what is the best way to block this pin.

Thanks,
I've done some experiments on a Kenko converter with both A contact, screw drive gear and SDM/Power zoom contacts. By removing (not covering, physically removing) one or severall of these camera-lens connections I tried to get SDM or screw drive outofocus to work on my DA*50-135.

Here are those of my conclusions that are relevant to your question:

"Somehow the K20D will not activate the screwdrive even without the chip because (me guessing what goes on in the K20D processor):
-with no A contacts at all it seas the lens/converter-combo as a K lens and does never activate the screwdrive (and not the SDM either in that modification combo)
-with the 6 old A contacts but without the 7th data contact, the camera seas the lens as a KA lens and does not activate any autofocus (because no such lens ever had autofocus)
-with all 7 A contacts and the screwdrive transfer in place but no SDM contacts it sees the lens as a F or FA lens...that was my biggest hope to activate the screwdrive...but the camera still does not activate the screwdrive...I assume it seas that it is a SDM lens (from some info sent by the 7th A contact) and activate the SMD (which does nothing since I disconnected it) not the screwdrive

So why does the SDM lens (DA*50-135) have a screwdrive connection at all?
To screwdrive focus on a camera without SDM!
Not to help me screwdrive focus through a modified converter!
Pentax put in preventions to avoid that, not trusting amateurs technicians like me or third party converter manufacturers that they would not happen to activate both SDM and screwdrive focus at the same time (which I carefully avoided), because it would probably seriously **** up the lens!!! Don't even want to think about what that could do to the poor lens!"

From: https://www.pentaxforums.com/forums/372705-post21.html

In the thread: https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/38514-converti...erter-sdm.html

05-29-2009, 12:44 PM   #5
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Original Poster
Thank you, SOldBear for the suggestion.

Douglas, thanks for sharing your experiment.
It's good to know.

Let me see what's going on with my Tamron 1.4x TC.
I'm not sure I will take it apart yet unless it's broken
but I'll see if I can test the contact using multimeter.

One thing you mentioned is that your Kenco 2x TC doesn't AF with DA*50-135 & K20D.

In my past experience with Tamron 1.4x TC +K20D + DA*16-50, it will lock focus only in VERY bright light. It struggles to locks even in decent light.
Actually I haven't tried it with DA*50-135 yet since I just got the lens 2 weeks ago.
Some reported the same AF problem with their K20D + Tamron 1.4xTC + DA* 50-135. It will move the SDM but with a hard time in locking focus.

Strange thing is Richard on DPReview reported that his Tamron 1.4xTC works so well with his new DA*60-250?
What's the difference between these lenses SDM?
Is Pentax applying different SDM technology?
05-29-2009, 01:11 PM   #6
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QuoteOriginally posted by HermanLee Quote

In my past experience with Tamron 1.4x TC +K20D + DA*16-50, it will lock focus only in VERY bright light. It struggles to locks even in decent light.

Strange thing is Richard on DPReview reported that his Tamron 1.4xTC works so well with his new DA*60-250?
My Tamron 1.4x works fine with both the DA* 16-50mm f2.8 and DA* 60-250mm f4.
Not that I ever use it with the 16-50mm though.
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