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02-09-2009, 03:39 PM   #1
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teleconverter question

Hi,
Here's a (hopefully) simple question for all you wonderful people who know more than me! (aka pretty much everyone on this forum)
Everything I read about teleconverters confuses me more and more, I was under the impression they would work on any lens with the appropriate mount. However, when I looked at the sigma website, it listed some lenses that were specially designed to work on teleconverters...

Does this mean that only some lenses work with teleconverters, or is this only an issue with sigma lenses/teleconverters?

I guess the reason I was asking was because I was looking into getting a DA 55-300 (to replace the 50-200 I'm borrowing). would there be any teleconverter that would work with the lens in question, or a reason why I wouldn't want to use a teleconverter on it?

Thanks in advance for your help!
Cheers,
Ryan

02-09-2009, 04:33 PM   #2
Damn Brit
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I think there are restrictions with some of the newer lenses due to the internal workings of them HSM motors etc.
You might find a TC in the Marketplace here. Pentax are supposed to be bringing out a new TC this year, they announced it last autumn. If you buy an older TC with a K mount, it should be fine on the 55-300. 1.4x would be better than a 2x, the 2x tends to degrade IQ more.
02-09-2009, 05:30 PM   #3
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QuoteOriginally posted by total.boredom Quote
Hi,
Here's a (hopefully) simple question for all you wonderful people who know more than me! (aka pretty much everyone on this forum)
Everything I read about teleconverters confuses me more and more, I was under the impression they would work on any lens with the appropriate mount. However, when I looked at the sigma website, it listed some lenses that were specially designed to work on teleconverters...

Does this mean that only some lenses work with teleconverters, or is this only an issue with sigma lenses/teleconverters?

I guess the reason I was asking was because I was looking into getting a DA 55-300 (to replace the 50-200 I'm borrowing). would there be any teleconverter that would work with the lens in question, or a reason why I wouldn't want to use a teleconverter on it?

Thanks in advance for your help!
Cheers,
Ryan

the sigma TC is a great TC, in both 1.4x and 2x BUT like some of the pentax rear converters, the front element of the TC actually sticks out and protrudes into the rear cavity of the lens. as a result it does not even work with 100% of all sigma lenses.

It is really designed specifically for long sigma tele's and zooms, like the 70-200 F2.8 and similar. It will also work on the pentax 300 F2.8, and 600 F4 lenses, and a few other sigma zooms, and long primes, but usually those with equal to 200 F2.8 or faster.
02-09-2009, 05:34 PM   #4
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QuoteOriginally posted by Lowell Goudge Quote
the sigma TC is a great TC, in both 1.4x and 2x BUT like some of the pentax rear converters, the front element of the TC actually sticks out and protrudes into the rear cavity of the lens. as a result it does not even work with 100% of all sigma lenses.

It is really designed specifically for long sigma tele's and zooms, like the 70-200 F2.8 and similar. It will also work on the pentax 300 F2.8, and 600 F4 lenses, and a few other sigma zooms, and long primes, but usually those with equal to 200 F2.8 or faster.
Would it work with the Pentax DA 55-300?
from what you said im guessing it won't but I'd figure I'd ask...

02-10-2009, 11:31 AM   #5
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QuoteOriginally posted by total.boredom Quote
Would it work with the Pentax DA 55-300?
from what you said im guessing it won't but I'd figure I'd ask...
I've not seen the rear element of the 55-300 so I can't say if it's compatible with the sigma (I'd guess it might not be), but instead of looking at the Sigma 1.4x consider the Tamron 1.4x or Kenko 1.5x (said to be very similar to each other). These will work with any k-mount lens as they don't have the protruding front element.
02-10-2009, 11:51 AM   #6
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for all those who are interested in the sigma TC's and compatibility with lenses, here is what I have, from the info sheets that came with my APO TC 1,4X EX and my APO TC 2X EX DG

Sigma APO Tele Macro 300 F4 (only MF for the 2x)
Sigma APO Tele Macro 400 F5.6 (only MF )
Sigma APO 70-200 F2.8
Pentax FA* 200mm F2.8 ED (IF)
Pentax FA* 300mm F2.8 ED (IF)
Pentax FA* 600mm F4 ED (IF) (only MF for the 2x)


by the time I bought my 2X DG version they added the following
SIGMA APO Macro 180mm F3.5 (mf only)
SIGMA APO 300mm F2.8 EX
SIGMA APO 500mm F4.5 EX (mf only)
SIGMA APO 800mm F5.6 EX (mf only)
SIGMA APO 50-5000mm F4-6.3 EX (mf only)
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