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08-07-2017, 06:05 AM   #1
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Teleconverters for k-1

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I'm looking for a 2x or similar teleconverter for my Tamron 70-200. I don't believe there's any that would allow me to keep af correct?

Out of the manual ones, which are better in terms of sharpness? I found a Sigma APO 2x converter on ebay, I guess it will allow me to af older Sigma glass (if I had any) but my Tamron would be manual? Does it reduce sharpness a lot?

There's a few vivitar series 1 2x converters, reviews on Amazon are rather mixed.

Basically need advice on a model) the Pentax HD one is out of my budget for now, so something around 50-150$ would work for me.

Thanks in advance)

08-07-2017, 07:24 AM   #2
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There are some that have all the connections to allow autofocus, even with an SDM lens. In practice, though, you have to be at large apertures to allow autofocus to work through the teleconverter.

First step when looking for a teleconverter -- make sure it's a 6 or 7 element design, and not a 4 element design. 4 element designs degrade image quality a lot more.

Here's an "autofocus" teleconverter: Teleplus 2x Autofocus / Pz-AF 2x Teleconverter For Pentax
08-07-2017, 09:36 AM   #3
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QuoteOriginally posted by timw4mail Quote
There are some that have all the connections to allow autofocus, even with an SDM lens. In practice, though, you have to be at large apertures to allow autofocus to work through the teleconverter.

First step when looking for a teleconverter -- make sure it's a 6 or 7 element design, and not a 4 element design. 4 element designs degrade image quality a lot more.

Here's an "autofocus" teleconverter: Teleplus 2x Autofocus / Pz-AF 2x Teleconverter For Pentax
Understood, thanks! This teleplus is same as kenko converters? Unfortunately that listing would arrive too late for the eclipse I want to shoot, but at least it gives me a reference point, thanks!
08-07-2017, 10:07 AM   #4
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QuoteOriginally posted by awscreo Quote
Understood, thanks! This teleplus is same as kenko converters? Unfortunately that listing would arrive too late for the eclipse I want to shoot, but at least it gives me a reference point, thanks!
I'm not sure, but they are very similar.

08-07-2017, 03:41 PM   #5
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I found two versions of kenko 7 element converter - "p-af 2x" and pz-af 2x". The pz listing mentions that it can af with sdm lenses. Would that work with my DFA 28-105? Or it will only work with Tamron 70-200?
08-07-2017, 03:54 PM   #6
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QuoteOriginally posted by awscreo Quote
I found two versions of kenko 7 element converter - "p-af 2x" and pz-af 2x". The pz listing mentions that it can af with sdm lenses. Would that work with my DFA 28-105? Or it will only work with Tamron 70-200?
The 'Pz' version has the power zoom contacts, which will enable it to work with SDM lenses. I'm pretty sure all of the pins are just a pass-through, so it should work with any lens that works on your camera. I would assume the other variant would only work with screwdrive lenses.
08-07-2017, 04:22 PM   #7
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QuoteOriginally posted by timw4mail Quote
The 'Pz' version has the power zoom contacts, which will enable it to work with SDM lenses. I'm pretty sure all of the pins are just a pass-through, so it should work with any lens that works on your camera. I would assume the other variant would only work with screwdrive lenses.
Hmm, makes sense. Thing is - I don't think I have any sdm glass, I have 3 af lenses, two are screw-drive (da 50 1.8 and Tamron 70-200) and DFA 28-105 uses another af method as far as I know, a plm motor? I'm leaning towards the p-af version as it's a third of the price, and in "as new" condition)

08-07-2017, 05:10 PM   #8
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QuoteOriginally posted by awscreo Quote
Hmm, makes sense. Thing is - I don't think I have any sdm glass, I have 3 af lenses, two are screw-drive (da 50 1.8 and Tamron 70-200) and DFA 28-105 uses another af method as far as I know, a plm motor? I'm leaning towards the p-af version as it's a third of the price, and in "as new" condition)
If it's not screwdrive, you'll need the "Pz" variant.
08-07-2017, 06:49 PM   #9
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QuoteOriginally posted by timw4mail Quote
If it's not screwdrive, you'll need the "Pz" variant.
But since 28-105 is 5.6 on the long end, it wouldn't work right? Is it f4 and wider for af to work? Sorry for all the questions, just want to make sure I'll buy the right thing) the pz variant is rather pricey, although cheaper than a new lens or the Pentax HD one)
08-07-2017, 06:54 PM   #10
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QuoteOriginally posted by awscreo Quote
But since 28-105 is 5.6 on the long end, it wouldn't work right? Is it f4 and wider for af to work? Sorry for all the questions, just want to make sure I'll buy the right thing) the pz variant is rather pricey, although cheaper than a new lens or the Pentax HD one)
You want to try to keep your setup to f5.6, because that's what most camera AF points are rated at, that's how you're getting the best out of your system, and remember, shooting wildlife or sport is difficult in the first place.

Having said that, I routinely shoot an FA*300 and 1.4TC which means f6.7 in total, and it's not bad.
08-07-2017, 07:02 PM   #11
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QuoteOriginally posted by clackers Quote
You want to try to keep your setup to f5.6, because that's what most camera AF points are rated at, that's how you're getting the best out of your system, and remember, shooting wildlife or sport is difficult in the first place.

Having said that, I routinely shoot an FA*300 and 1.4TC which means f6.7 in total, and it's not bad.
I'm just torn between the p-af version ($50) and pz-af ($160) I guess I'm gonna have to get the pz one just to use it with any glass I have, not just the two screw drive ones I own
08-07-2017, 07:42 PM   #12
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QuoteOriginally posted by awscreo Quote
I'm just torn between the p-af version ($50) and pz-af ($160) I guess I'm gonna have to get the pz one just to use it with any glass I have, not just the two screw drive ones I own
To be honest, Awscreo, I found these older Sigma or Tamron/Kenko TCs could deteriorate image quality to the point I could crop the original image and it would be similar.

The Pentax HD one I use now is pricey but good.

08-07-2017, 07:45 PM   #13
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I have a Kenko Teleplus PZ 1.5X TC. Yes, it will auto-focus with SDM and DC lenses. I have tried it with a DA*50-135mm, DA*300mm and DA 18-135mm, the latter two which I own. With these motorized lenses, it was slow (lots of hunting) and worse yet, it was unreliable. The camera (K20D and K-3) confirmed focus when the subject was out of focus.

My Kenko 1.5X is a very nice TC with my Tamron 70-200, D FA 100mm macro and any of my screw drive lenses. Like all TC's it compromises auto-focus speed, but IQ is very good. (My Kenko is actually a 1.4X, same design as the PZ version of the Tamron 1.4X. The true Kenko 1.5X is supposedly a weaker lens.)

I have a Pentax HD 1.4X RC. The Kenko is close enough in performance that I use it with without hesitation on some of my screw drive lenses. I have used both TC's together to mimic a 2X, and IQ was not pretty. I have owned a Pentax Rear Converter-A 2x-S and a Vivitar A-2X. The Pentax was bad and the Vivitar was dreadful. It is my firm opinion that 2X TC's are not a good idea.

Last edited by audiobomber; 08-08-2017 at 04:09 AM.
08-07-2017, 08:11 PM   #14
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QuoteOriginally posted by audiobomber Quote
I have a Kenko Teleplus PZ 1.5X TC. Yes, it will auto-focus with SDM and DC lenses. I have tried it with a DA*50-135mm, DA*300mm and DA 18-135mm, the latter two which I own. With these motorized lenses, it was slow (lots of hunting) and worse yet, it was unreliable. The camera (k20D and K-3) confirmed focus when the subject was out of focus.

My Kenko 1.5X is a very nice TC with my Tamron 70-200, D FA 100mm macro and any of my screw drive lenses. Like all TC's it compromises auto-focus speed, but IQ is very good. (My Kenko is actually a 1.4X, same design as the PZ version of the Tamron 1.4X. The true 1.5X is supposedly a weaker lens.)

I have a Pentax HD 1.4X RC. The Kenko is close enough in performance that I use it with without hesitation on some of my screw drive lenses. I have used both TC's together to mimic a 2X, and IQ was not pretty. I have owned a Pentax Rear Converter-A 2x-S and a Vivitar A-2X. The Pentax was bad and the Vivitar was dreadful. It is my firm opinion that 2X TC's are not a good idea.
Hmm, reviews on pf for that tc seem to be generally positive, with only negatives going towards af. Originally I wanted to shoot the eclipse, and was thinking to get a 400+ vintage lens, but suddenly though maybe a tc would be better and more useful with my other lenses. I'm torn lol. Has anyone tried that kenko tc? The 1.4 is cheaper so less painful to gamble on
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