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08-16-2007, 07:56 AM   #1
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Some questions about Tele Converters

I am hoping that some of you can point me in the proper direction on this. I'm considering buying a tele converter. Without going into to much boring background, I'm trying to find out if there is really any major diference between these four tele converters.

Kenko x1.5 DG AF
Sigma x1.4 APO DG
Sigma x1.4 APO (Non DG)
Tamron x1.4 AF

I have read that the Sigma tele converters are for specific sigma lenses. Should I assume that they will not work with lenses not on the "approved list"?

Is there any significant diference between the Sigma DG and the non DG version?

I have read that people claim the Kenko and Tamron are identical except for the branding. is this true?

I have a Sigma 50-500 coming in a few days. Is the Sigma DG so much better than the others to justify the added expense?

Will the Tamron (or any of the others) work just as well on the Bigma?

The only lenses that I can actually see me using this on is the Bigma if I need a bit extra range, an FA 50 f1.4, and a Tamron 28-75 f2.8.

Thanks in advance for any help.

08-16-2007, 08:54 AM   #2
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I can't answer any of the questions regarding sigma, but I can vouch for the Tamron being a very good teleconverter. I've used it with my FA*400mm f/5.6 lens. It retains autofocus and the quality of the image is not noticably diminished.

Here's one example where I know I used the teleconverter (EXIF data doesn't change when it's used):



Hope this helps.
08-16-2007, 09:43 AM   #3
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I have the Sigma 50-500 (non dg) and my understanding is that the newer dg lens has a different coating specific for digital. Not sure if there is a big difference but I suspect not.

I have the 1.4x converter matched for the non dg version of the bigma I have. The tc is nice but you lose AF. If you go this route, with the bigma, you will have to expand the lens to at least 100mm before the tc will fit on the lens. It will not fit at the 50mm setting.

I can't speak for the tamron or kenko but I do not think tc's are compatible with any lenses under 100mm. I know the Sigma is not and thus will not fit on those other lenses you mentioned.
08-20-2007, 07:05 AM   #4
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If I was to couple a TC with the Sigma lens I'd go with the Sigma TC. I don't know what it is but it seems like they "match" their TC's to their lenses and the IQ loss is minimal. I used Sigma 70-200EX (non DG) with their 2xTC (non DG) for wildlife shots (until I got my Tokina AT-X 400) and the IQ loss very little (see the birds gallery in my pbase account for samples)

Now the only thing with the Sigma TC's is that the element of the TC sticks out, so if you use it on another brand lens (or unapproved Sigma lens) it is possible that the TC element will hit the rear Lens element damaging both. Be very careful and check that they won't touch before using it on a lens that is not on the approved list.

All the TC's you mention will work on the bigma, I do have the Kenko 1.5x but have only used a few times, with decent results see this example: Bald Eagle with a Salmon for dinner photo - palmor photos at pbase.com

Oh, try a search on pbase for the bigma with a TC, you may get some hits back and be able to judge if it is something you'd want to do.

Hope that helps
John


QuoteOriginally posted by Mr Hyde Quote
I am hoping that some of you can point me in the proper direction on this. I'm considering buying a tele converter. Without going into to much boring background, I'm trying to find out if there is really any major diference between these four tele converters.

Kenko x1.5 DG AF
Sigma x1.4 APO DG
Sigma x1.4 APO (Non DG)
Tamron x1.4 AF

I have read that the Sigma tele converters are for specific sigma lenses. Should I assume that they will not work with lenses not on the "approved list"?

Is there any significant diference between the Sigma DG and the non DG version?

I have read that people claim the Kenko and Tamron are identical except for the branding. is this true?

I have a Sigma 50-500 coming in a few days. Is the Sigma DG so much better than the others to justify the added expense?

Will the Tamron (or any of the others) work just as well on the Bigma?

The only lenses that I can actually see me using this on is the Bigma if I need a bit extra range, an FA 50 f1.4, and a Tamron 28-75 f2.8.

Thanks in advance for any help.


08-20-2007, 06:36 PM   #5
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Thanks John. You really hit the nail on the head with your answer. Your suggestion gave me an avenue for some research. Thanks again
08-20-2007, 07:17 PM   #6
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On thing you have to worry about from the different manufacturers is how the TCs are made. Some TCs have a lens that juts out into the lens mount, others are made flush or recessed into the TC.

This physical construction is a worry on some lenses. For example, the Bigma has a lock feature that will not allow the rear element from crashing into the TC when focusing or zooming. The Bigma is a rear focus lens. Some TCs do not fit the lens as well as others.

I have a Tamron 2X Bbar TC that seems to fit everything I can to it simply because there aren't any elements that jut out. Canon TCs are bad for this, as are some of the other manufacturers.

Just something to look for.
08-21-2007, 08:46 PM   #7
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Thanks for all the replies. I'm still in the decision making mode but for now I'm leaning toward the tamron 1.4 since I know I can use it for everything. if it doesnt suit my purposes I'll just ebay it and try the Sigma APO 1.4
08-22-2007, 01:16 AM   #8
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Hullo Andrew!
Terrific picture of a sparrow! Justy wondering how a 400mm/f5.6 lens + TC (even if just 1.4x) permits AF?! Effective aperture becomes f8 and I know of very few SLRs (none Pentax) that AF at f8. (I am presuming you use Pentax; could just as well be the Canon EOS-3 or 1V!!)
Bharat.

08-22-2007, 05:05 AM   #9
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QuoteOriginally posted by Khukri Quote
Hullo Andrew!
Terrific picture of a sparrow! Justy wondering how a 400mm/f5.6 lens + TC (even if just 1.4x) permits AF?! Effective aperture becomes f8 and I know of very few SLRs (none Pentax) that AF at f8. (I am presuming you use Pentax; could just as well be the Canon EOS-3 or 1V!!)
Bharat.
A f/5.6 lens with 1.4x TC will still autofucus (it does on my K10) but you do need to have bright conditions and it is slower (and may hunt if less then ideal light). I have used this combo to catch Eagles in flight (see link in my previous post), but the conditions where nice and bright.



John
08-22-2007, 10:28 PM   #10
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Hullo John!

That is a very nice picture of the eagle! Happy to know the K10D can be so sensitive! Now all I need to do if figure out whether to buy the K10D now or wait for the new model to come as rumoured by year end!
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