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05-29-2012, 12:25 PM   #1
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Teleconverter recommendation needed

Hi All,

I am looking for a high-quality 1.4 or 2.0X teleconverter to use with my DA* 60-250 telezoom lens mounted on a K-5 camera. From reading reviews, it seems not all teleconverters fit the K-5 mount. If anyone has a recommendation for a properly fitting teleconverter I would be most appreciative.

05-29-2012, 12:40 PM   #2
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QuoteOriginally posted by wjax Quote
Hi All,

I am looking for a high-quality 1.4 or 2.0X teleconverter to use with my DA* 60-250 telezoom lens mounted on a K-5 camera. From reading reviews, it seems not all teleconverters fit the K-5 mount. If anyone has a recommendation for a properly fitting teleconverter I would be most appreciative.
Obviously, the teleconverter needs to be made for "Pentax K" mount (not Nikon or Canon or Minolta, et.c). All Pentax-mount teleconverters will fit on the K-5...

Whether they also fit on your DA*60-250 is a different story. Any Pentax-brand teleconverter that has an "L" after it (such as "Pentax Rear Converter-A 2x-L") will not fit, as it has a big protruding element. The ones labeled "S" (as in "Pentax Rear Converter-A 2x-S") will fit, but are generally not as good quality. Also, these are all manual-focus teleconverters, regardless whether your lens has its own AF motor or not.

When it comes to "other brands," the current Sigma teleconverters for Pentax are optically very good, but will only drive a screwdrive lens, so your DA*60-250mm will revert to being a screwdrive (not ultrasonic motor) lens... and even then the focusing might not work. Sigma generally says your lens needs to be f/4 or brighter to AF with the 1.4x TC, and f/2.8 or brighter to AF with the 2x TC. (Essentially, if there is too much glass darkening the view, your AF sensors can't "see" well enough to focus!)

Finally, there are older (used) teleconverters for Pentax from various manufacturers with the label "Pz-AF" in their name, which means "Powerzoom - AutoFocus." They have the contacts to send the (old Power zoom) SDM focusing signals from the camera to the lens, so you retain the native ultrasonic AF on your DA*60-250. I have Tamron-branded Pz-AF teleconverters (both 1.4x and 2x) and the 1.4x is an excellent TC that retains AF even on my slow Sigma 150-500 @500mm (f/6.3)!

Last edited by panoguy; 05-29-2012 at 12:57 PM.
05-29-2012, 12:41 PM   #3
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First of all, let me begin by saying that only pentax K mount compatible teleconverters have any chance of fitting on any pentax DSLR, not all of which will fit your lens, not so much the camera.

What you need to consider however is that not all telecovnerters will let you autofocus, even if they are autofocusing teleconverters, due to the speed of your lens. For AF to work reliably you need to have the combined maximum aperture of the lens plus TC at F6.9 or faster. A combined F8 aperture may be too slow to focus reliably except in very bright conditions

Next, although sigma makes some very good 1.4x and 2x teleconverters, these are generally not compatible with any lens other than sigma very fast teles and zooms, due to the optical design. to use one of these requires the lens have a rear element recessed at least 12mm and the lens throat at least 35mm inside diameter. They will also work on some pentax and tamron fast lenses but not many.

tamron makes a good all round teleconverter, as did kenko, and there are some new ones labelled vivitar (Probably samyang) that get favourable reports.

You can also possibly use the pentax 1.7x AF TC but again look out for the lens speed.

what is your aim, in terms of subject
05-29-2012, 01:03 PM   #4
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QuoteOriginally posted by Lowell Goudge Quote
You can also possibly use the pentax 1.7x AF TC but again look out for the lens speed.
Lowell caught the one I forgot about. The Pentax Autofocus Adapter (AFA) 1.7x is a pretty good teleconverter that *replaces* the autofocusing of your lens (the AFA has moving elements), instead of driving the lens AF. What this means is that any K-mount lens (whether AF or MF) can be mounted in front of the 1.7x AFA and you just manually focus the main lens close to your intended subject and then press the AF button (or shutter half-press) and the camera will tell the teleconverter to move its own lenses to get the final focus.

I have one of these, and while the AF is admirably fast and effective, the quality isn't as good as my Tamron Pz-AF. C'est la vie!

05-29-2012, 01:09 PM   #5
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i have both the tamron 1.4 and the pentax 1.7...they both slow down autofocus but i have better chance of catching something moving fast with the pentax...the tamron seems to work ok for the 60-250 but doesn't work well with the 300...overall i have been able to use the pentax for the majority of my lens and for the most part am quite happy with the results..amy
05-29-2012, 05:06 PM   #6
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I recommend the Tammy 1.4 Pz-AF. I have the two Sigmas and the Pentax 1.7. The Tammy (and the identical Kenko 1.5) work consistently, whereas the others are quirky.

Russ
05-30-2012, 07:11 AM   #7
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QuoteOriginally posted by oeriies Quote
I recommend the Tammy 1.4 Pz-AF.
Do you know where I could find one? I don't see one currently listed for sale here or at ebay. Thanks!!
05-30-2012, 09:57 AM   #8
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I am looking also.

05-30-2012, 11:03 AM   #9
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Be a little patient, or place a "Wanted" ad here (seems coreyhkh already has). At one point last month there were 3 Pz-AF TCs listed on the marketplace here (from different sellers).
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