Convert Pentax 1.7x to AF extension tube

chiepapi · 11-05-2016, 08:10 PM

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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?

Adam · 11-05-2016, 08:13 PM

Originally posted by chiepapi

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.

**boriscleto** · 11-05-2016, 09:11 PM

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...

chiepapi · 11-05-2016, 09:34 PM

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😁

Wild Mark · 11-06-2016, 03:27 AM

You would do better to sell the adapter and buy a Kenko Unitube

robthebloke · 11-06-2016, 06:38 AM

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.

pathdoc · 11-06-2016, 06:40 AM

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).

**Lowell Goudge** · 11-06-2016, 07:56 PM

Originally posted by chiepapi

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

chiepapi · 11-06-2016, 08:39 PM

Originally posted by Lowell Goudge

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.

gabriel_bc · 11-06-2016, 11:24 PM

Originally posted by chiepapi

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.

11-05-2016, 08:10 PM	#1
chiepapi Veteran Member Join Date: Feb 2009 Location: AZ Posts: 308	Convert Pentax 1.7x to AF extension tube Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here. 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
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,609	Originally posted by chiepapi 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. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

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11-05-2016, 09:11 PM	#3
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,477	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
chiepapi Veteran Member Join Date: Feb 2009 Location: AZ Posts: 308 Original Poster	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
Wild Mark Veteran Member Join Date: Jun 2013 Location: Newcastle Photos: Gallery \| Albums Posts: 1,954	You would do better to sell the adapter and buy a Kenko Unitube

11-06-2016, 06:38 AM	#6
robthebloke Veteran Member Join Date: Sep 2013 Location: Sydney Photos: Albums Posts: 844	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
pathdoc Pentaxian Join Date: Mar 2015 Photos: Gallery \| Albums Posts: 6,381	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
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,892	Originally posted by chiepapi 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
chiepapi Veteran Member Join Date: Feb 2009 Location: AZ Posts: 308 Original Poster	Originally posted by Lowell Goudge 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
gabriel_bc Veteran Member Join Date: Sep 2009 Location: Langley, BC Photos: Gallery Posts: 550	Originally posted by chiepapi 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.