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zzeitg · 05-17-2015, 03:19 PM

Just wondering... is there any 3rd party 2x TC which would support AF on Pentax SDM lenses?

vonBaloney · 05-17-2015, 03:40 PM

It seems like the Tamron one would (that has the correct contacts) work for SDM, but reports are that it doesn't. I haven't heard of one that does (for SDM). There are some that work for screw drive if the light is bright enough (and the base lens is fast enough). I have one (Vivitar 2x MC7) that has screw-drive pass-through and has SDM contacts on one side only (not sure why). Works fine with screw-drive lenses, but the SDM (actually Sigma HSM) lenses I've tried I can't even mount it -- the camera immediately freaks out and freezes up. The AFA 1.7x is an interesting option -- not quite 2x, but it provides its own AF for any lens (with a little manual help)...

MadMathMind · 05-17-2015, 03:56 PM

Yes. I have one I have been trying to unload for a while (Marketplace posting link) Tamron makes one. It has SDM contacts and works in theory--my Sigma 70-200 spins around trying to get focus but doesn't. But it doesn't work with the 1.4 either. The only SDM lens I have is the DA*300, which doesn't work with the TC because it's too slow.

Otherwise, the TC will autofocus. Works well with the FA50 f/1.7. The FA77 gets there eventually, but it sorta creeps its way up there.

vonBaloney · 05-17-2015, 04:13 PM

Originally posted by MadMathMind

It has SDM contacts and works in theory

From what I've heard, all of the 2x's that "work in theory" don't work in practice for SDM (even though the Tamron 1.4x with all the contacts generally works fine with SDM). I'd be interested to hear if anyone has actually ever gotten any SDM/HSM lens to autofocus with any 2x TC...

krazykat · 05-17-2015, 04:47 PM

Originally posted by vonBaloney

From what I've heard, all of the 2x's that "work in theory" don't work in practice for SDM (even though the Tamron 1.4x with all the contacts generally works fine with SDM). I'd be interested to hear if anyone has actually ever gotten any SDM/HSM lens to autofocus with any 2x TC...

The Tamron x2 TC that I sold on the Marketplace worked perfectly with my Sigma 17-50 HSM.

vonBaloney · 05-17-2015, 05:54 PM

Originally posted by krazykat

The Tamron x2 TC that I sold on the Marketplace worked perfectly with my Sigma 17-50 HSM.

Yay! That's the Pz-AF model?

krazykat · 05-17-2015, 10:52 PM

Originally posted by vonBaloney

Yay! That's the Pz-AF model?

It was the BBAR MC7.

05-17-2015, 03:19 PM	#1
zzeitg Pentaxian Join Date: Sep 2014 Location: South Bohemia Photos: Gallery \| Albums Posts: 4,017	2x TC with AF support (incl. SDM) Just wondering... is there any 3rd party 2x TC which would support AF on Pentax SDM lenses?

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05-17-2015, 03:40 PM	#2
vonBaloney Pentaxian Join Date: Oct 2011 Location: Albuquerque, NM Posts: 6,029	It seems like the Tamron one would (that has the correct contacts) work for SDM, but reports are that it doesn't. I haven't heard of one that does (for SDM). There are some that work for screw drive if the light is bright enough (and the base lens is fast enough). I have one (Vivitar 2x MC7) that has screw-drive pass-through and has SDM contacts on one side only (not sure why). Works fine with screw-drive lenses, but the SDM (actually Sigma HSM) lenses I've tried I can't even mount it -- the camera immediately freaks out and freezes up. The AFA 1.7x is an interesting option -- not quite 2x, but it provides its own AF for any lens (with a little manual help)...

05-17-2015, 03:56 PM	#3
MadMathMind Veteran Member Join Date: Dec 2013 Location: Houston, TX Photos: Gallery Posts: 1,717	Yes. I have one I have been trying to unload for a while (Marketplace posting link) Tamron makes one. It has SDM contacts and works in theory--my Sigma 70-200 spins around trying to get focus but doesn't. But it doesn't work with the 1.4 either. The only SDM lens I have is the DA*300, which doesn't work with the TC because it's too slow. Otherwise, the TC will autofocus. Works well with the FA50 f/1.7. The FA77 gets there eventually, but it sorta creeps its way up there.

05-17-2015, 04:13 PM	#4
vonBaloney Pentaxian Join Date: Oct 2011 Location: Albuquerque, NM Posts: 6,029	Originally posted by MadMathMind It has SDM contacts and works in theory From what I've heard, all of the 2x's that "work in theory" don't work in practice for SDM (even though the Tamron 1.4x with all the contacts generally works fine with SDM). I'd be interested to hear if anyone has actually ever gotten any SDM/HSM lens to autofocus with any 2x TC...

05-17-2015, 04:47 PM	#5
krazykat Veteran Member Join Date: Aug 2010 Posts: 546	Originally posted by vonBaloney From what I've heard, all of the 2x's that "work in theory" don't work in practice for SDM (even though the Tamron 1.4x with all the contacts generally works fine with SDM). I'd be interested to hear if anyone has actually ever gotten any SDM/HSM lens to autofocus with any 2x TC... The Tamron x2 TC that I sold on the Marketplace worked perfectly with my Sigma 17-50 HSM.

05-17-2015, 05:54 PM	#6
vonBaloney Pentaxian Join Date: Oct 2011 Location: Albuquerque, NM Posts: 6,029	Originally posted by krazykat The Tamron x2 TC that I sold on the Marketplace worked perfectly with my Sigma 17-50 HSM. Yay! That's the Pz-AF model?

05-17-2015, 10:52 PM	#7
krazykat Veteran Member Join Date: Aug 2010 Posts: 546	Originally posted by vonBaloney Yay! That's the Pz-AF model? It was the BBAR MC7.

2x TC with AF support (incl. SDM)

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