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12-27-2011, 07:28 AM   #1
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Tele converter. Need help

Hi there!
Yet another tc question. A month ago I bought a Sigma 70-200mm F2.8 APO HMSII, and I would like to add a tc.

I get confuse reading the sigma's tele converter matching list (http://www.sigma-photo.co.jp/english/acc/condaitr.htm), so that I ask for help:
  • will the autofocus work or will it only be in the manual focus mode ?
  • What about the quality ?
  • Is there any better option rather tan sigma tc?
I'll appreciate any kind of advice from you

Cheers

12-27-2011, 07:41 AM   #2
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I don't believe the sigma tc for Pentax supports hsm, so no, the AF won't work. I personally haven't heard of any sdm-compatible converters, although theoretically they should be fairly simple to make.

If you had a tamron 70-200 it would work using the screwdrive, I think.
12-27-2011, 07:49 AM   #3
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Adam, you've never heard that the PZ-AF tamron teleconverters will AF with SDM/HSM lenses?!

The tamron PZ-AF BBAR 1.4x teleconverter as well as the Tamron 2x MC7 BBAR PZ-AF will work with the HSM. I tried both when I had the sigma 120-400mm HSM OS lens - they will both hunt somewhat, but worked better (more reliable) with the HSM lens than they do with my 50-135mm SDM lens (which is faster than the 120-400mm, f2.8 compared to f4-5.6). Considering the 120-400mm is a much slower lens than the 70-200mm F2.8, it would be at least worth a try with one of those converters (the 1.4x converter will probably give the best/most reliable results).

As Adam indicated, Sigma's teleconverters will not autofocus with their Pentax mount HSM lenses.
12-27-2011, 07:58 AM   #4
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QuoteOriginally posted by Adam Quote
I don't believe the sigma tc for Pentax supports hsm, so no, the AF won't work. I personally haven't heard of any sdm-compatible converters, although theoretically they should be fairly simple to make.

If you had a tamron 70-200 it would work using the screwdrive, I think.

So, focus would be manual. Sorry I forgotten to ask, Which F number will be the minimum i.e. F4, F5.6?

Thanks Adam for your answer.



12-27-2011, 08:05 AM   #5
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QuoteOriginally posted by pxpaulx Quote
Adam, you've never heard that the PZ-AF tamron teleconverters will AF with SDM/HSM lenses?!

The tamron PZ-AF BBAR 1.4x teleconverter as well as the Tamron 2x MC7 BBAR PZ-AF will work with the HSM. I tried both when I had the sigma 120-400mm HSM OS lens - they will both hunt somewhat, but worked better (more reliable) with the HSM lens than they do with my 50-135mm SDM lens (which is faster than the 120-400mm, f2.8 compared to f4-5.6). Considering the 120-400mm is a much slower lens than the 70-200mm F2.8, it would be at least worth a try with one of those converters (the 1.4x converter will probably give the best/most reliable results).

As Adam indicated, Sigma's teleconverters will not autofocus with their Pentax mount HSM lenses.
Ok pxpaulx from your experience I'll better try a tamron teleconverter rather than to get a sigma one, Am I right?
Thanks
12-27-2011, 08:40 AM   #6
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The funny thing is that the Sigma converter(s) with the protruding front element apparently work with the Tamron 70-200 1:2.8 (Canon version: Tamron SP AF 70-200 mm f/2.8 Di LD (IF) MACRO review - Build quality - Lenstip.com, bottom of page) (?).
12-27-2011, 09:02 AM   #7
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QuoteOriginally posted by Ogion Quote
Ok pxpaulx from your experience I'll better try a tamron teleconverter rather than to get a sigma one, Am I right?
Thanks
Yeah the PZ-AF BBAR versions of the 1.4x and 2x Tamron teleconverters are your best bet. The term PZ-AF refers to powerzoom - this was an older feature on some Pentax film camera lenses. The neat thing is that the same 2 contacts that were used to enable the powerzoom feature are the same contacts that are currently used to run SDM (on pentax lenses) and HSM (on your sigma lens). Since you asked, the 1.4x TC will add 1 stop, making the lens approximately 100-280mm F4, while the 2x converter adds 2 stops, making the lens approximately 140-400mm F5.6.
12-27-2011, 11:20 AM   #8
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QuoteOriginally posted by pxpaulx Quote
Yeah the PZ-AF BBAR versions of the 1.4x and 2x Tamron teleconverters are your best bet. The term PZ-AF refers to powerzoom - this was an older feature on some Pentax film camera lenses. The neat thing is that the same 2 contacts that were used to enable the powerzoom feature are the same contacts that are currently used to run SDM (on pentax lenses) and HSM (on your sigma lens). Since you asked, the 1.4x TC will add 1 stop, making the lens approximately 100-280mm F4, while the 2x converter adds 2 stops, making the lens approximately 140-400mm F5.6.
Thank you pxpaulx for your help and clear explanation

Chears

01-05-2012, 06:02 AM   #9
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Hi
I was near to buy a tamron tc but....I woundering if somebody has tested/experience on a Vivitar 2x7-P TC. I fount it on ebay but I don't know, again, if AF would work.

Thanks for your help
01-05-2012, 07:55 AM   #10
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Haven't seen that teleconverter before...unfortunately the photo doesn't show that it has the powerzoom contacts. They are located on the interior of the mount, so could be on the side not shown in the photo.
01-05-2012, 08:08 AM   #11
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QuoteOriginally posted by pxpaulx Quote
Haven't seen that teleconverter before...unfortunately the photo doesn't show that it has the powerzoom contacts. They are located on the interior of the mount, so could be on the side not shown in the photo.
You're right, on Vivtar web site images dosen't help that much, but aparentely contacs are inside.
01-05-2012, 08:21 AM   #12
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This Vivitar will definitely not work with AF, ever through SDM or screw.

There are no electric contacts on the mount (see here : http://www.aohc.it/images/k1e.gif ) means it is only manual TC...
01-05-2012, 12:31 PM   #13
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QuoteOriginally posted by lepiallou Quote
This Vivitar will definitely not work with AF, ever through SDM or screw.

There are no electric contacts on the mount (see here : http://www.aohc.it/images/k1e.gif ) means it is only manual TC...
Hi lepaillou
Have you used this TC? I'm asking just because the vendor claim that "The converters will work completely with the auto-focus mechanisms of the camera as long as the maximum aperture on the primary lens is f3.5 or wider. If the aperture is slower, the in-focus lights will work but focusing must be done manually"
01-05-2012, 05:54 PM   #14
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I don't claim to be an expert on the K mounts and the variants but I do believe that the Autofocus models need contacts to interact with the electronics of the camera. A TC needs to pass those signals through from the body to the lens and back in order for them to interact. The picture in the ad is of a plain K mount without any such contacts. The diagram below has been of help to me in looking at lenses online because sellers are often wrong - whether intentionally or unintentionally doesn't matter.

And a picture of one that is also listed as a Vivitar that has all the contacts.

Last edited by Docrwm; 05-06-2013 at 08:11 PM.
01-06-2012, 12:17 AM   #15
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QuoteOriginally posted by Ogion Quote
I'm asking just because the vendor claim that
Well the vendor also claim that it is "Optimized for Mega Pixel Photography, Suppresses Aberrations, Weather Resistant" !!!

And as mentionned Docrwm electric contacts are necessary to use any AF lens...
So either the picture is not from the actual TC, either the TC is worth less than 20$

Maybe you can ask to the vendor another picture?
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