1.4x rear converter and Sigma 70-200mm?

**tmacdon** · 06-26-2014, 09:15 AM

Has anyone tried the new HD Pentax-DA 1.4x AW AF Rear Converter with the (widely-used) Sigma 70-200mm f/2.8 (EX DG APO OS HSM)? Quite simply, does the HSM autofocus work?

The reviews are unclear, and I imagine that anyone who tries the two will know immediately. I have a new K3 body, if that matters.

**pearsaab** · 06-26-2014, 04:37 PM

for whatever it's worth I tried it on the sigma 50-500 apo ex hsm os ( the latest version of the bigma) and it doesn't work...it might occasionally lock in but it is struggling trying to find focus...tried with os on and off and it didn't matter..i don't have the 70-200 but suspect with the hsm and os it would respond the same

**nater** · 06-26-2014, 05:38 PM

Sigma 50-500mm experience won't be useful, that lens is f/4.5-6.3 and because of that won't AF well with any teleconverter. I believe the rule of thumb is don't use a 1.5x teleconverter on a lens slower than f/4.

normhead · 06-26-2014, 06:25 PM

When I asked about a telelconverter for my Sigma 70-300, the guy said "It won't work and don't try it." The 70-200 was the lens I wanted, he suggest the 70-200 with the 2x. One of my buddies has that and it's a real nice combo. But I'd get the 2x to go with the 2.8 lens. That gets you to 400 5.6, pretty decent.

**ROBEFFY** · 06-26-2014, 08:45 PM

Originally posted by normhead

When I asked about a telelconverter for my Sigma 70-300, the guy said "It won't work and don't try it." The 70-200 was the lens I wanted, he suggest the 70-200 with the 2x. One of my buddies has that and it's a real nice combo. But I'd get the 2x to go with the 2.8 lens. That gets you to 400 5.6, pretty decent.

Hi Normhead,
I have a Sigma 70-200 APO HSM DG, bought about 6 years ago, and AF did not work with the TC I tried at Henry's, both a 1.4 and a 2.0 TC. I don't remember if they were Sigma or Pentax TC units.

So, Your buddy has a 2x TC, who makes it? Sigma or Pentax? I would really like to get one. I believe Sigma says on their site that their 70-200 does not support AF on a Pentax with their TC?

400 and 5.6 is just fine!

**crewl1** · 06-26-2014, 09:22 PM

The Pentax HD 1.4x does not allow autofocus with the Sigma 70-200 2.8 OS.
Lens will hunt and not achieve focus.

Same results with the Sigma 50-500 OS.

I have tested it.

normhead · 06-27-2014, 03:34 AM

Originally posted by ROBEFFY

Hi Normhead,
I have a Sigma 70-200 APO HSM DG, bought about 6 years ago, and AF did not work with the TC I tried at Henry's, both a 1.4 and a 2.0 TC. I don't remember if they were Sigma or Pentax TC units.

So, Your buddy has a 2x TC, who makes it? Sigma or Pentax? I would really like to get one. I believe Sigma says on their site that their 70-200 does not support AF on a Pentax with their TC?

400 and 5.6 is just fine!

My buddy with the combo shoots Canon, so this could well be true.

**tmacdon** · 06-29-2014, 08:35 AM

Thanks folks...this is very clear, and thus very helpful. I will simply have to live without the 1.4 converter on an upcoming trip.

06-26-2014, 09:15 AM	#1
tmacdon Site Supporter Join Date: Apr 2008 Location: Cambridge, MA Posts: 143	1.4x rear converter and Sigma 70-200mm? Has anyone tried the new HD Pentax-DA 1.4x AW AF Rear Converter with the (widely-used) Sigma 70-200mm f/2.8 (EX DG APO OS HSM)? Quite simply, does the HSM autofocus work? The reviews are unclear, and I imagine that anyone who tries the two will know immediately. I have a new K3 body, if that matters.

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06-26-2014, 04:37 PM	#2
pearsaab Otis Memorial Pentaxian Loyal Site Supporter Join Date: May 2011 Location: Richmond, Virginia USA Photos: Gallery \| Albums Posts: 2,900	for whatever it's worth I tried it on the sigma 50-500 apo ex hsm os ( the latest version of the bigma) and it doesn't work...it might occasionally lock in but it is struggling trying to find focus...tried with os on and off and it didn't matter..i don't have the 70-200 but suspect with the hsm and os it would respond the same

06-26-2014, 05:38 PM	#3
nater Loyal Site Supporter Join Date: Aug 2009 Location: New England Photos: Albums Posts: 706	Sigma 50-500mm experience won't be useful, that lens is f/4.5-6.3 and because of that won't AF well with any teleconverter. I believe the rule of thumb is don't use a 1.5x teleconverter on a lens slower than f/4.

06-26-2014, 06:25 PM	#4
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	When I asked about a telelconverter for my Sigma 70-300, the guy said "It won't work and don't try it." The 70-200 was the lens I wanted, he suggest the 70-200 with the 2x. One of my buddies has that and it's a real nice combo. But I'd get the 2x to go with the 2.8 lens. That gets you to 400 5.6, pretty decent.

06-26-2014, 08:45 PM	#5
ROBEFFY Site Supporter Join Date: Sep 2009 Location: Northern Ontario Photos: Gallery Posts: 248	Originally posted by normhead When I asked about a telelconverter for my Sigma 70-300, the guy said "It won't work and don't try it." The 70-200 was the lens I wanted, he suggest the 70-200 with the 2x. One of my buddies has that and it's a real nice combo. But I'd get the 2x to go with the 2.8 lens. That gets you to 400 5.6, pretty decent. Hi Normhead, I have a Sigma 70-200 APO HSM DG, bought about 6 years ago, and AF did not work with the TC I tried at Henry's, both a 1.4 and a 2.0 TC. I don't remember if they were Sigma or Pentax TC units. So, Your buddy has a 2x TC, who makes it? Sigma or Pentax? I would really like to get one. I believe Sigma says on their site that their 70-200 does not support AF on a Pentax with their TC? 400 and 5.6 is just fine!

06-26-2014, 09:22 PM	#6
crewl1 Site Supporter Join Date: Jul 2010 Location: Los Angeles, CA Photos: Gallery \| Albums Posts: 9,807	The Pentax HD 1.4x does not allow autofocus with the Sigma 70-200 2.8 OS. Lens will hunt and not achieve focus. Same results with the Sigma 50-500 OS. I have tested it.

06-27-2014, 03:34 AM	#7
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	Originally posted by ROBEFFY Hi Normhead, I have a Sigma 70-200 APO HSM DG, bought about 6 years ago, and AF did not work with the TC I tried at Henry's, both a 1.4 and a 2.0 TC. I don't remember if they were Sigma or Pentax TC units. So, Your buddy has a 2x TC, who makes it? Sigma or Pentax? I would really like to get one. I believe Sigma says on their site that their 70-200 does not support AF on a Pentax with their TC? 400 and 5.6 is just fine! My buddy with the combo shoots Canon, so this could well be true.

06-29-2014, 08:35 AM	#8
tmacdon Site Supporter Join Date: Apr 2008 Location: Cambridge, MA Posts: 143 Original Poster	Thanks folks...this is very clear, and thus very helpful. I will simply have to live without the 1.4 converter on an upcoming trip.