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09-02-2010, 08:31 PM   #16
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No AF, but the Pentax A1.4X-L should provide the best optical match.

09-03-2010, 08:25 AM   #17
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Kenko 1.5 may be available

I own a copy of the Tamron 1.4x and recently bought (and sold) a Promaster Spectrum 1.7 teleconverter, which looked identical apart from the optics. It's my understanding that Kenko took over the manufacture of these units from Tamron and that their 1.5X unit is very similar to the Tamron 1.4X. A few of the Kenkos have been available through the marketplace here recently and the Promaster show up from time to time.

Be aware that these teleconverters have the power-zoom contacts (PZ) that enables the newer HSM/SDM lenses to focus. However, since this wasn't the intended use of the teleconverters, it can be hit or miss. I find the Sigma 120-400 HSM focuses reliably, but a little slowly, others report some lenses have difficulty focusing. The teleconverters also make no correction for the focal length, which will degrade shake reduction.

Otherwise, the optics of the 1.4x and 1nd 1.5x seem to be good.

Mike
09-03-2010, 09:58 AM   #18
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QuoteOriginally posted by Stringmike Quote
Be aware that these teleconverters have the power-zoom contacts (PZ) that enables the newer HSM/SDM lenses to focus. However, since this wasn't the intended use of the teleconverters, it can be hit or miss. I find the Sigma 120-400 HSM focuses reliably, but a little slowly, others report some lenses have difficulty focusing. The teleconverters also make no correction for the focal length, which will degrade shake reduction.
I have had several copies of the Tamron 1.4x and they all worked with my SDM lenses, but depending on the lens, the degree of success varied (there didn't seem to be any difference between the different copies of the 1.4x).

In order, I found that the DA*300 worked the best with the 1.4x. The DA*200 and DA*60-250 also worked well, although it would often take a second attempt to lock focus if you weren't close to start. The DA*50-135 worked with the TC, but the least well of the DA* lenses I owned. It almost always requiring a second or third attempt to lock focus.
09-03-2010, 03:18 PM   #19
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QuoteOriginally posted by wlachan Quote
No AF, but the Pentax A1.4X-L should provide the best optical match.
Isn't that tc designed for lenses over 300mm?

Edit: Pentax Imaging still has some of these in stock. $525.95. wowcb The list it for these lenses. I wonder if it will work with the DA* 300mm or 60-250mm.

http://www.pentaxwebstore.com/detail/PTX+30943

QuoteQuote:
  • Compact dimensions
  • For FA 250-600mm, FA 300mm, FA 600mm, A 300mm, A 500mm, A 600mm, A 1200mm, K 400mm, K600mm
  • SMC reduce internal reflections for optimum performance
  • Maintains all Program Modes
  • Manual Focus only with all lenses



Last edited by Blue; 09-03-2010 at 04:23 PM.
09-04-2010, 03:57 PM   #20
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QuoteOriginally posted by Blue Quote
Isn't that tc designed for lenses over 300mm?
Not exactly. The L converters will fit teles with recessed rear element like FA/DA*200/2.8 too. F*300/4.5, DA*300/4, DA*50-135/2.8 & DA*60-250/4 don't have recessed rear element so L converters won't fit.
09-19-2010, 10:12 AM   #21
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I own both the Kenko 1.5X and the Pentax 1.7X AF TC's.
Both work with my DA*16-50mm and my DA*60-250mm. Even at night (K-7).
The Kenko works with SDM and the Pentax uses it's own internal focusing mechanism.
I find it hard to believe that they do not work with the DA*200mm.
The Pentax will work with any lens.

Focusing with those TC's can be a problem with slow lenses in low light like the DA18-250.

- Bert
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