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11-05-2016, 08:10 PM   #1
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Convert Pentax 1.7x to AF extension tube

I've seen posts that mentioned a DYI extension tube by recycling a beaten up TC by removing the glass. I'm wondering if someone has done this with the AF1.7x?

11-05-2016, 08:13 PM   #2
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QuoteOriginally posted by chiepapi Quote
I've seen posts that mentioned a DYI extension tube by recycling a beaten up TC by removing the glass. I'm wondering if someone has done this with the AF1.7x?
If you did that you would lose the AF functionality, because the 1.7x is an AF adapter that doesn't require the lens mounted on it to support AF. You'd still get auto aperture, though.

On the other hand, the glass removal trick would work with any TC that passes through the AF driveshaft and/or SDM contacts.

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11-05-2016, 09:11 PM   #3
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Get something like the Quantaray 2x TC. It has SDM contacts as well as the screw drive...

Quantaray 2x Teleconverter AF auto focus teleextender Lens for PENTAX cameras 81097260263 | eBay

I don't know if it's worth $80. I paid like $25 for mine...
11-05-2016, 09:34 PM   #4
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Thanks guys. I already have the 1.7x that I'm thinking of experimenting on. I'll think it over again. Don't want to end up with another paper weight😁

11-06-2016, 03:27 AM   #5
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You would do better to sell the adapter and buy a Kenko Unitube
11-06-2016, 06:38 AM   #6
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Kooka 25mm AF extension tubes exist, and can be bought new. Unless you are intending to use a lens that is quickshift, don't bother. When (and trust me you will) want to fall back to manual focus, the sound of the lens driving the AF coupling in the extension tube will probably make you cry. With a quickshift lens it's just about workable, although personally I think you'd be better off with a manual focus tube that supports the A contacts.
11-06-2016, 06:40 AM   #7
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The glass in the 1.7 is essential to the AF function, as it is what transforms manual focus lenses to AF once you get close enough. Deglassing it would be a waste. Get a cheap one like a used Kenko or Kalimar; the optics don't matter after all.

Out of interest, I'd like to know from anyone who does have a third-party K mount AF teleconverter whether it passes all the EXIF, focal length and MTF data from the newer lenses. I know my current Kalimar P-KA/R does not. (I was happy to go with P-KA only rather than AF because macro shooters often turn it off anyway).
11-06-2016, 07:56 PM   #8
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QuoteOriginally posted by chiepapi Quote
Thanks guys. I already have the 1.7x that I'm thinking of experimenting on. I'll think it over again. Don't want to end up with another paper weight😁
At the value of the 17x adaptor you would be foolish to tamper with it.. Get a piece of junk to try this with. I would suggest any 2x tc

11-06-2016, 08:39 PM   #9
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QuoteOriginally posted by Lowell Goudge Quote
At the value of the 17x adaptor you would be foolish to tamper with it.. Get a piece of junk to try this with. I would suggest any 2x tc
I don't know the value of my 1.7x adapter anymore since the glass has marks in it that's why I thought of tweaking it than having it cleaned - if at all still possible. It's posted in the marketplace in case you're curious what it looks like.
But yes. I get it now. There's no point removing the glass to make an AF extender since it's the main reason it can AF.
11-06-2016, 11:24 PM   #10
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QuoteOriginally posted by chiepapi Quote
I don't know the value of my 1.7x adapter anymore since the glass has marks in it that's why I thought of tweaking it than having it cleaned - if at all still possible. It's posted in the marketplace in case you're curious what it looks like.
But yes. I get it now. There's no point removing the glass to make an AF extender since it's the main reason it can AF.
I would send your 1.7 AF adapter to Brian for a CLA - his handle on the forum is dcshooter. He can get that adapter cleaned up to be as good as it can be.
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