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04-21-2018, 03:05 PM   #1
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Which teleconverter??

So I have a Tamron 70-200 that I used for kids sports and any other opportunity I can find to use it. I'm planning on doing a few air shows this year and it's just a little short. So I'm looking for a teleconverter since I don't want to get a new lens this year. So which one would you suggest?

Da 1.4x or Fa 1.7x AF?

I could use the extra reach of the 1.7x but one day I might add the DA* 300 and the 1.4x would be a better match. But I think that's a few years away, if ever, realistically.

04-21-2018, 03:10 PM   #2
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If you're shooting APS-C, I'd go for the 1.4x. The native AF is easier to work with in general, and the image quality is top-notch.

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04-21-2018, 03:15 PM   #3
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QuoteOriginally posted by ncallender Quote
Da 1.4x or Fa 1.7x AF?
The Pentax 1.7x is not a TC but rather an autofocus adapter. SMC Pentax-F 1.7x AF Adapter Reviews - Pentax K-mount Teleconverters and Adapters - Pentax Lens Reviews & Lens Database

It was originally designed to add autofocus to Pentax manual focus lenses. It does work as a TC as well just keep in mind you have to manually focus close then finish with the AF of the adapter.

In most cases the DA 1.4x RC is the one you want.
04-21-2018, 03:17 PM - 1 Like   #4
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Check this out:

Pentax K-Mount Teleconverter Guide - Articles and Tips | PentaxForums.com

The FA 1.7 is probably not a good choice. It has a limited AF range. I have that autofocus adapter, a Tamron 1.4 and 2. The 1.4 is used most since you loose less light and autofocus works a bit better. I would guess you will happier with the DA 1.4.

04-21-2018, 04:13 PM   #5
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I own both and an FA* 300 and the DA* 60-250. As mentioned they are different. In an air show the 1.7x may be offer some benefits as a focus limiter.
04-21-2018, 06:47 PM   #6
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I'm using the 1.7x on my K-1 (and K3II) as a TC, even though it takes over the focus part. I've really only used it on the K-1 for comparison to upsampling with a 150-450, and it's mixed - some shots with the TC were better at certain apertures, and some upsampled were better. There is a bit of CA and purple fringing that gets introduced, but that's easy to take care of in post. If you shop, you can find them at about half the price of the 1.4x, but even though I've not shot with the 1.4x, from everything I can tell from other's reviews, it's going to be better optically. The 1.7x is screw drive, and not the quickest on focus speed, but not terrible. If you have legacy manual focus lenses, now you have autofocus. I'd say if you like to play, watch for one at a good price and go for it, but if you could only buy one and had to stick with the choice and were only doing APS-C, I'd think the 1.4x is going to be better.

Last edited by clickclick; 04-21-2018 at 07:06 PM.
04-21-2018, 06:52 PM - 1 Like   #7
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For air shows etc. I'd stick with the 1.4. The 1.7 can be really irritating when refocusing is required.

04-21-2018, 07:33 PM - 1 Like   #8
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Ok, thanks folks. I think the DA 1.4x is there right way to go. Now to find one before the first air show!
04-22-2018, 07:16 AM - 1 Like   #9
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I've been quite happy with my Tamron 1.4 teleconverter and I've used it with a number of lenses. I bought it used on the Marketplace. It's pretty highly rated as seen in the reviews found at the following forum link. The average rating is almost identical to the average rating for the DA 1.4 but if you find one it will probably be at lower cost.

Tamron-F 1.4X Pz-AF MC4 Lens Reviews - Miscellaneous Lenses - Pentax Lens Review Database
04-22-2018, 07:37 AM   #10
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QuoteOriginally posted by ncallender Quote
Da 1.4x or Fa 1.7x AF?
I have both. The 1.7x is great under the right conditions but it can be finiky and it eats light. I use the 1.4x 90% of the time.
04-22-2018, 09:07 AM   #11
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QuoteOriginally posted by dave2k Quote
I've been quite happy with my Tamron 1.4 teleconverter and I've used it with a number of lenses. I bought it used on the Marketplace. It's pretty highly rated as seen in the reviews found at the following forum link. The average rating is almost identical to the average rating for the DA 1.4 but if you find one it will probably be at lower cost.

Tamron-F 1.4X Pz-AF MC4 Lens Reviews - Miscellaneous Lenses - Pentax Lens Review Database
This is the one I have, and it lives on my 300 F4!
04-22-2018, 12:34 PM   #12
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I also use Tamron 1.4x - this is good TC, which supports full frame and both 'screwdriver' and SDM autofocus.
04-22-2018, 07:00 PM   #13
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QuoteOriginally posted by pentageek Quote
I also use Tamron 1.4x - this is good TC
Yes it is.
04-22-2018, 07:15 PM   #14
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QuoteOriginally posted by dadipentak Quote
I have both. The 1.7x is great under the right conditions but it can be finiky and it eats light. I use the 1.4x 90% of the time.
My use is about the same. There are times you need the extra reach, but you really reduce your odds of getting even one image with moving subjects..
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