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09-08-2010, 03:06 PM   #1
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PK/A extension tubes?

Can you find these anywhere? Looked at the bay and elsewhere, but no luck. Preferably something in the 20 - 30mm range, or more.

09-08-2010, 03:36 PM   #2
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Without electrical contacts a set of 3 that combined are 50mm can be found online for $10 and up. Assuming you are looking for a set WITH contacts it can be a long search and not cheap. Some members recommend just finding a 1.4x TC with bad glass and good contacts and remove the glass, voila a 20-30mm (my guess) tube with contacts.
09-08-2010, 04:14 PM   #3
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QuoteOriginally posted by imtheguy Quote
Some members recommend just finding a 1.4x TC with bad glass and good contacts and remove the glass, voila a 20-30mm (my guess) tube with contacts.
Like the one on the right (actually from a 2X TC):

09-08-2010, 04:24 PM   #4
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QuoteOriginally posted by SOldBear Quote
Like the one on the right (actually from a 2X TC):
Eggs-actly!

09-11-2010, 03:39 PM   #5
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Thanks guys,

Yeah I am looking for the ones with contacts. Bummer. Then I guess it is off to the bay looking for a PKA tele converter. But if I remember correctly these ones doesn't come that cheap either.
09-11-2010, 05:52 PM   #6
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In the picture posted by SOldBear the 13mm extension is part of a set of three PK/A extension rings (13, 20, 36mm) made by Vivitar. Vivitar made one without contacts but even that one was called an automatic extension ring set so finding one can be pretty confusing as well.
05-25-2012, 05:01 AM   #7
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imtheguy: Sorry if this is a dumb question, but how would one go about removing the glass (and still leave the contacts working :-)

As it happens I have just such a cheap 1.4x K-mount extension tube... [Edit: Sorry I meant TC not extension tube]

Last edited by tonyrodgers; 05-26-2012 at 06:29 AM.
05-25-2012, 06:21 AM - 1 Like   #8
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I've been watching this thread. There is an inexpensive solution that doesn't take a lot of mechanical ability or time to implement. The catch is that it works only for a specific lens. As many macro shooters always use the same lens, this shouldn't be a big deal.

There are two steps to use any PK-mount lens with aperture controls (sorry, no DA lens) on manual PK-mount extension tubes as though it was a directly mounted 'A' lens with full in-camera metering. #1- make your camera think that all lens are 'A' lens, and #2- tell your camera what your lens minimum and maximum aperture values are.

It takes five minutes to fool your Pentax dSLR into thinking all mounted lens are 'A' capable. It is totally reversible, but I have yet to have a reason to do so. It doesn't interfere with any of my lens.
https://www.pentaxforums.com/forums/pentax-k-r/178928-kr-short-contacts-chang...ml#post1867401

Next, you have to do some minor alteration to the extension tube that is directly mounted to the camera body. Again, it is reversible if need be. If you are using multiple tubes, you probably only need to do this to your shortest tube, and always mount that one to the camera body first. But it is no big deal one way or the other if you modify all your tubes.
#1- remove any insulating paint from the tube's mounting flange. This will cause all the contacts on the camera body to be shorted (other than the 'A' contact, but you fixed that with the above instructions).
#2- note the minimum and maximum apertures for your lens. Go to this site and use the matrix to determine which contacts should be insulated so they are not shorted.
#3- DON'T use the site's advice to drill shallow divots in your extension tube mount. Sure it works, but the change is permanent.
#4- use very narrow pieces of magic tape to mark which contacts need to be insulated. Place them on the camera body so they are seen outside the mounting flange.
#5- mount the extension tube you prepared in step 1 without insulation on the mounting flange. Now take additional narrow pieces of magic tape and stick them on the side of the tube carefully aligned with the pieces of tape on the camera body.
#6- unmount the extension tube. Place a small piece of magic tape on the mounting flange carefully aligned with the tape on the side of the extension tube. This tape should be no wider than the lens contact point on the body.
#7- remove the tape from the camera body. Carefully remove the tape from the sides of the extension tube. Make sure the tape on the extension tube mounting flange is tightly pressed into place. Trim away any excess tape.

When you mount the extension tube on the body, I suggest pressing in the lens release button before seating and turning the tube. Once the tube is fully seated, release the button and turn the tube backward to make sure it is locked in place. This seems to minimize the chance that you will rip the insulating pieces of tape off the extension tube. Mount the other tubes and/or lens.

Set your lens to its maximum aperture. Meter your subject. Note the aperture shown on your camera body, and set a matching aperture on the camera lens. You don't need to adjust for the light loss caused by the tubes. Your camera will assume it is simply a darker subject. If you do need to adjust exposure it will be for the standard artistic reasons.

05-25-2012, 09:51 AM   #9
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QuoteOriginally posted by tonyrodgers Quote
Sorry if this is a dumb question, but how would one go about removing the glass (and still leave the contacts working :-)

As it happens I have just such a cheap 1.4x K-mount extension tube...
If you look into the TC you should see that the glass is held in by a ring with a couple small slots in it. The slots are opposite each other. I use a lens spanner to engage those slots and unscrew the ring. Some folks use a drafting compass, or a thin metal strip or ruler, anything that can fit into both slots. Some cheap TCs (and 1.4x TCs usually aren't the cheapest) may have the glass glued in or held with a molded piece. In such a case, too bad, unless you feel like shooting a .22 slug at it.
05-25-2012, 11:02 AM   #10
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Sharp Fiskar sewing scissors used as spanner wrench for removing filter element or TC lens assembly.

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05-25-2012, 11:36 AM - 1 Like   #11
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make your own auto tube, follow-up

My instructions read longer than the actual modifications. So I thought I'd send some photos to show how easy this is.

I am not using extension tubes, but a Panagor macro zoom adapter. The optics and mount were designed for a Pentax M 50mm lens, so this is pretty much what you would get using plain K-mount tubes except for the automatic stop down of the lens from wide-open to the preset f/stop during exposure. I happen to be using a Pentax A 50mm f/1.7 lens, and my K-r body acts the same as if that lens were directly mounted. This lens has an aperture range of f/1.7 to f/22. The chart says I only need to insulate the #2 contact to let my camera know this.

The first photo is the paired lens and macro adapter.
The second photo is the plugged 'A' contact on my K-r (I've never found any reason to unplug this contact, but it literally takes less than 5 minutes to do so).
The third photo is the mounting flange of the macro adapter with the insulating piece of magic tape. I colored it purple to show up better in the photo.
Attached Images
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PENTAX K-r  Photo 
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05-26-2012, 06:31 AM   #12
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thanks RioRice & Newarts - I have successfully removed the glass from a K-mount Kenko 2x MC4 - now to do some testing...
06-01-2012, 04:41 PM   #13
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Why doesn't any company today produce true auto pentax (PK) extension tubes? A quick search on amazon lists several brands for canikon at affordable (sub 100 dollar for 3x sets).. but even pentax today doesn't invest in creating such an accessory. its a bummer.
06-01-2012, 04:52 PM   #14
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QuoteOriginally posted by mee Quote
Why doesn't any company today produce true auto pentax (PK) extension tubes? A quick search on amazon lists several brands for canikon at affordable (sub 100 dollar for 3x sets).. but even pentax today doesn't invest in creating such an accessory. its a bummer.
Tiny % of people interested in it from a brand with a small market share. As that share grows again, we'll see more third-party accessories.
06-01-2012, 06:12 PM   #15
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QuoteOriginally posted by vonBaloney Quote
Tiny % of people interested in it from a brand with a small market share. As that share grows again, we'll see more third-party accessories.
Might help if Pentax-Ricoh licensed manufacture of adapters and other accessories, to be made by firms meeting PRIC's quality standards. I suspect some items are already licensed -- PRIC likely doesn't make their own batteries, remotes, sensor-cleaning kit, etc. So, why not licensed TCs; macro tubes and other extension; T/S and M42-PK and M39-PK and and T2 and mount-reversal and other adapters; filters; etc. Licensees will have motivation to push their goods at competitive prices, while bearing the Pentax brand. Should be a win-win: Pentaxians get quality accessories at reasonable cost whilst Pentax gets brand-name promotion (and a cut of the take) yet doesn't have to run more production lines.

Last edited by RioRico; 06-01-2012 at 06:20 PM.
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