Macro Pentax Auto Focus Extension Tubes

**pntxjack** · 05-20-2014, 08:08 AM

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If you are here (PF), you probably know this trick. I am not the inventor, but I came up with the idea independently.
Pentax does not make an AF extension tube, nor does anyone else in the Pentax mount.
What to do?
Get an AF rear converter, remove all of the glass VOILA, a Pentax mount AF extension tube!
1.4x = ~ 18mm of extension, 2x = ~ 25mm of extension. I have combined them for ~ 43mm of extension.
The shorter the focal length of the lens, the greater the effect of the extension.
Enjoy.
Jack

maltfalc · 05-21-2014, 02:20 AM

or you can get a manual focus / auto aperture teleconverter, remove the glass and spend a couple hours with a dremel adding an extra data pin and a screw drive connection like i did.

Not a Number · 06-02-2014, 06:59 PM

It looks like Kooka Optics in China are making AF extension tubes for K-mount. They make a 25mm and a 20 + 36mm set. There doesn't appear to be anybody in the US at the moment selling these but there are vendors in the UK and Germany selling 25mm tube.

www.kooka-optics.com

**RKKS08** · 06-08-2014, 04:26 AM

Jessop (UK based, I think) obviously has offered such tubes.
On German eBay, a used set is offered. The pictures show, that at least the 31mm tube supports AF.
The 13mm and 21mm ones don't.

Auction will end in less than 4 hours.

Jessop Extension Tube Set for Pentax K & KA-Bayonet mount | eBay

**Digitalis** · 06-08-2014, 05:11 AM

I have a set of extension tubes that support screw-drive and SDM focusing, however you would have to be rather stupid to try using AF at magnifications at 1:2 and beyond. Even my D4 doesn't reliably get the focus right at 1:1 and that camera has the most advanced AF module of any camera I own.

05-20-2014, 08:08 AM	#1
pntxjack Site Supporter Join Date: Mar 2008 Location: placerville, ca Photos: Gallery \| Albums Posts: 171	Pentax Auto Focus Extension Tubes 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. If you are here (PF), you probably know this trick. I am not the inventor, but I came up with the idea independently. Pentax does not make an AF extension tube, nor does anyone else in the Pentax mount. What to do? Get an AF rear converter, remove all of the glass VOILA, a Pentax mount AF extension tube! 1.4x = ~ 18mm of extension, 2x = ~ 25mm of extension. I have combined them for ~ 43mm of extension. The shorter the focal length of the lens, the greater the effect of the extension. Enjoy. Jack

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05-21-2014, 02:20 AM	#2
maltfalc Veteran Member Join Date: May 2010 Location: Winnipeg Photos: Albums Posts: 396	or you can get a manual focus / auto aperture teleconverter, remove the glass and spend a couple hours with a dremel adding an extra data pin and a screw drive connection like i did.

06-02-2014, 06:59 PM	#3
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	It looks like Kooka Optics in China are making AF extension tubes for K-mount. They make a 25mm and a 20 + 36mm set. There doesn't appear to be anybody in the US at the moment selling these but there are vendors in the UK and Germany selling 25mm tube. www.kooka-optics.com

06-08-2014, 04:26 AM	#4
RKKS08 Site Supporter Join Date: Mar 2010 Location: Frankfurt am Main Posts: 1,241	Jessop (UK based, I think) obviously has offered such tubes. On German eBay, a used set is offered. The pictures show, that at least the 31mm tube supports AF. The 13mm and 21mm ones don't. Auction will end in less than 4 hours. Jessop Extension Tube Set for Pentax K & KA-Bayonet mount \| eBay

06-08-2014, 05:11 AM	#5
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	I have a set of extension tubes that support screw-drive and SDM focusing, however you would have to be rather stupid to try using AF at magnifications at 1:2 and beyond. Even my D4 doesn't reliably get the focus right at 1:1 and that camera has the most advanced AF module of any camera I own.