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pcarfan · 03-02-2009, 07:07 PM

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I have this old Takumar-A 2X tele-converter pictured here

Asahi Pentax Takumar-A 2X Teleconverter, Case, LN, NR! - eBay (item 200315825023 end time Mar-08-09 21:33:05 PDT)

It is a poor performer and I don't use it. Is there a way to remove the internal lens elements and use it as a macro extension tube with A contacts.
Thank you.

ghost · 03-02-2009, 07:38 PM

A pick Axe/hammer?

Vylen · 03-03-2009, 02:03 AM

Originally posted by ghost

A pick Axe/hammer?

or a brick...

really.. you just have to be experimental... see if stuff screws off.. see if there's a screw here or there...

otherwise, glass + solid object = results

**Douglas_of_Sweden** · 03-03-2009, 02:16 AM

Originally posted by pcarfan

I have this old Takumar-A 2X tele-converter pictured here

Asahi Pentax Takumar-A 2X Teleconverter, Case, LN, NR! - eBay (item 200315825023 end time Mar-08-09 21:33:05 PDT)

It is a poor performer and I don't use it. Is there a way to remove the internal lens elements and use it as a macro extension tube with A contacts.
Thank you.

Yes, it is possible.
But as far as I can see from the smallish pic on the ebay add, this converter is a six contact version (KA mount, Features and Operation of the Ka Mount), meaning that the later added 7th contact is missing (KA2 or KAF mounts, Features and Operation of the Kaf Mount). The camera will read minimum apperture from the lens/tube version and enable Tv and P modes, but it is the 7th contact that communicates most of the info between lens and body: focal length, exact apperture, multi-segment meetering, some flash functions, subject distance etc. With this "tube" without the 7th contact nothing of this will work. Perhaps you are oK with this, or else look for one with 7 contacts.

pcarfan · 03-03-2009, 05:05 AM

Originally posted by Douglas_of_Sweden

Yes, it is possible.
But as far as I can see from the smallish pic on the ebay add, this converter is a six contact version (KA mount, Features and Operation of the Ka Mount), meaning that the later added 7th contact is missing (KA2 or KAF mounts, Features and Operation of the Kaf Mount). The camera will read minimum apperture from the lens/tube version and enable Tv and P modes, but it is the 7th contact that communicates most of the info between lens and body: focal length, exact apperture, multi-segment meetering, some flash functions, subject distance etc. With this "tube" without the 7th contact nothing of this will work. Perhaps you are oK with this, or else look for one with 7 contacts.

Thank you for this info, I'll look into it more.....

**Lowell Goudge** · 03-03-2009, 07:05 AM

the issue will be as follows.

the elements will come out in either one or 2 groups. BUT this will leave a big circular assembly in the middle that may not be willing to come out. You may need to disassemble both sides of the TC (i.e. mounts) to get this out, and this plate may also be needed to hold the apature activating lever. I have one that has a wonderful ball bearing movement for the lever, along with some springs, all of which pivot around the opening for the lens groups. If you cut this portion out, you may also compromise the automatic apature, leaving you with a lens attachment that has the A mode contacts but no ability to control the apature with the camera

pcarfan · 03-03-2009, 05:30 PM

I tried it, it didn't work as well. The lens element doesn't quite fall apart but all sorts of springs and levers do

Anyhow, destroyed the inside to finally remove the internal elements and put all the springs back in place (got the mount bent a bit, but it can be mounted but not fully seated).

However, once installed I am surprised how close I have to get to the subject to get it in focus. The dof is razor thin. Focusing on the lens pretty much does nothing. The very short subject distance and the thin DOF makes these extension tubes non-suitable for me. So, at least I know extension tubes are not an option for me, thanks to this TC. The end caps will be put to use .

**Lowell Goudge** · 03-03-2009, 05:33 PM

What focal length did you try for a lens.

If I recall correctly the TC was about 22 mm thick, therefore with kit lens you could get better than 1:1 at shorter focal lengths.

Remember for 1:1 you need extension equal to focal length.

SOldBear · 03-03-2009, 07:21 PM

Originally posted by pcarfan

However, once installed I am surprised how close I have to get to the subject to get it in focus. The dof is razor thin. Focusing on the lens pretty much does nothing. The very short subject distance and the thin DOF makes these extension tubes non-suitable for me. So, at least I know extension tubes are not an option for me, thanks to this TC.

What's the focal length of the lens?

The subject distance and the DOF are just the laws of physics. They apply to macro photography, no matter how you get to it.

I have a 60 macro lens. At 1:1 magnification, the subject is about 2" from the front of the lens. A 100mm macro lens, also at 1:1 magnification, gives me about 9" from the front of the lens to the subject.

Roughly, to get to 1:1 magnification, you need to bring the lens out from the camera body a distance as great as the focal length of the lens. So to get to 1:1, a 60mm lens needs 60mm tube and a 100mm lens needs 100mm tube.

An 18mm lens needs only 18mm tube to get to 1:1. But the subject practically touches the lens.

For setup with extension tube, the focusing mechanism on the lens doesn't do a whole lot. It's easier to move the whole setup back and forth. A macro focusing rail on a tripod is of great help.

DOF is always a problem. When you close down the aperture to get decent DOF, you don't have enough light. That's why you also need a flash, preferrably one with variable output.

pcarfan · 03-04-2009, 06:05 AM

It's a 50mm lens.

It's a 1:2 macro. Does this native magnification matter on what a 25mm long extension tube would do ? so what is the final magnification on a 50mm 1:2 macro with a 25mm extension tube ?

Thanks

P.S: I know about the dof being razor thin even before, never the less, it is just amazing to see it first hand. I was trying it from f2.8 all the way to f16 (max), and was fine at f16, but I am not interested in using this particular lens anything other than F2.8 or F4...I am just working on all possible use for this lens with it's quirkiness.

roentarre · 03-04-2009, 01:27 PM

Moved to accessory section.

SOldBear · 03-04-2009, 02:20 PM

Originally posted by pcarfan

It's a 50mm lens.

It's a 1:2 macro. Does this native magnification matter on what a 25mm long extension tube would do ? so what is the final magnification on a 50mm 1:2 macro with a 25mm extension tube ?

I apologize if I ask wrong questions here....

Are you sure the 50mm is a macro lens capable of 1:2 magnification? If it is, adding a 25mm will bring the magnification to 1:1, or very close to that.

What I'm afraid of is that the lens is a 50mm 1:2 lens. 1:2 here means f/2, the largest aperture, having nothing to do with macro.

A macro lens in most cases will have the word "macro" somewhere on the lens. A macro lens will extend significantly at close focus. See photos below:

Infinity focus:

At 1:1 magnification:

It does not matter how good the lens is, at macro range, F/2.8 - F/4.0 is not very practical.

**Lowell Goudge** · 03-04-2009, 02:54 PM

your lens is apparently, at least, 1:2 macro, it is truely a macro lens based upon the photos you show with the extension of the group when focused close,

I also like the apature scale showing the apparant apature change when you focus out, very useful for flash work.

As for final magnification ratio, assuming lens is 1:2 yes 25 mm would probably take you to 1:1,

pcarfan · 03-04-2009, 03:58 PM

It is a f2.8 1:2 macro lens, I am sure of it. It is the Volna-9. I know A-contacts are usually useless with M42 lenses, but I have a plan

But, now I can see how this ext. tube would be useful to get close with certain subjects, so I will keep this frankenstein extender for such occasions.

SOldBear · 03-04-2009, 04:15 PM

Originally posted by pcarfan

It is a f2.8 1:2 macro lens, I am sure of it..

Sorry for doubting you. On some forum here, someone asks whether the SMC Pentax-M 50mm 1:2 has 1:2 magnification....

With a 1:2 macro lens, the extension tube is still useful. Many macro lenses can go 1:2, and come with an extension tube to get to 1:1.

03-02-2009, 07:07 PM	#1
pcarfan Veteran Member Join Date: Sep 2007 Location: Dayton, Ohio Photos: Gallery \| Albums Posts: 2,978	Can I convert a TC into an extension tube with A contacts 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 have this old Takumar-A 2X tele-converter pictured here Asahi Pentax Takumar-A 2X Teleconverter, Case, LN, NR! - eBay (item 200315825023 end time Mar-08-09 21:33:05 PDT) It is a poor performer and I don't use it. Is there a way to remove the internal lens elements and use it as a macro extension tube with A contacts. Thank you.

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03-02-2009, 07:38 PM	#2
ghost Senior Member Join Date: Jan 2008 Location: Barrie, ON Photos: Gallery Posts: 174	A pick Axe/hammer?

03-03-2009, 02:03 AM	#3
Vylen Veteran Member Join Date: Dec 2008 Location: Sydney, Australia Photos: Gallery Posts: 1,262	Originally posted by ghost A pick Axe/hammer? or a brick... really.. you just have to be experimental... see if stuff screws off.. see if there's a screw here or there... otherwise, glass + solid object = results

03-03-2009, 02:16 AM	#4
Douglas_of_Sweden Site Supporter Join Date: Apr 2008 Location: Stockholm Photos: Gallery Posts: 3,374	Originally posted by pcarfan I have this old Takumar-A 2X tele-converter pictured here Asahi Pentax Takumar-A 2X Teleconverter, Case, LN, NR! - eBay (item 200315825023 end time Mar-08-09 21:33:05 PDT) It is a poor performer and I don't use it. Is there a way to remove the internal lens elements and use it as a macro extension tube with A contacts. Thank you. Yes, it is possible. But as far as I can see from the smallish pic on the ebay add, this converter is a six contact version (KA mount, Features and Operation of the Ka Mount), meaning that the later added 7th contact is missing (KA2 or KAF mounts, Features and Operation of the Kaf Mount). The camera will read minimum apperture from the lens/tube version and enable Tv and P modes, but it is the 7th contact that communicates most of the info between lens and body: focal length, exact apperture, multi-segment meetering, some flash functions, subject distance etc. With this "tube" without the 7th contact nothing of this will work. Perhaps you are oK with this, or else look for one with 7 contacts.

03-03-2009, 05:05 AM	#5
pcarfan Veteran Member Join Date: Sep 2007 Location: Dayton, Ohio Photos: Gallery \| Albums Posts: 2,978 Original Poster	Originally posted by Douglas_of_Sweden Yes, it is possible. But as far as I can see from the smallish pic on the ebay add, this converter is a six contact version (KA mount, Features and Operation of the Ka Mount), meaning that the later added 7th contact is missing (KA2 or KAF mounts, Features and Operation of the Kaf Mount). The camera will read minimum apperture from the lens/tube version and enable Tv and P modes, but it is the 7th contact that communicates most of the info between lens and body: focal length, exact apperture, multi-segment meetering, some flash functions, subject distance etc. With this "tube" without the 7th contact nothing of this will work. Perhaps you are oK with this, or else look for one with 7 contacts. Thank you for this info, I'll look into it more.....

03-03-2009, 07:05 AM	#6
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,891	the issue will be as follows. the elements will come out in either one or 2 groups. BUT this will leave a big circular assembly in the middle that may not be willing to come out. You may need to disassemble both sides of the TC (i.e. mounts) to get this out, and this plate may also be needed to hold the apature activating lever. I have one that has a wonderful ball bearing movement for the lever, along with some springs, all of which pivot around the opening for the lens groups. If you cut this portion out, you may also compromise the automatic apature, leaving you with a lens attachment that has the A mode contacts but no ability to control the apature with the camera

03-03-2009, 05:30 PM	#7
pcarfan Veteran Member Join Date: Sep 2007 Location: Dayton, Ohio Photos: Gallery \| Albums Posts: 2,978 Original Poster	I tried it, it didn't work as well. The lens element doesn't quite fall apart but all sorts of springs and levers do Anyhow, destroyed the inside to finally remove the internal elements and put all the springs back in place (got the mount bent a bit, but it can be mounted but not fully seated). However, once installed I am surprised how close I have to get to the subject to get it in focus. The dof is razor thin. Focusing on the lens pretty much does nothing. The very short subject distance and the thin DOF makes these extension tubes non-suitable for me. So, at least I know extension tubes are not an option for me, thanks to this TC. The end caps will be put to use .

03-03-2009, 05:33 PM	#8
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,891	What focal length did you try for a lens. If I recall correctly the TC was about 22 mm thick, therefore with kit lens you could get better than 1:1 at shorter focal lengths. Remember for 1:1 you need extension equal to focal length.

03-03-2009, 07:21 PM	#9
SOldBear Veteran Member Join Date: Feb 2009 Location: Alameda, CA Posts: 3,206	Originally posted by pcarfan However, once installed I am surprised how close I have to get to the subject to get it in focus. The dof is razor thin. Focusing on the lens pretty much does nothing. The very short subject distance and the thin DOF makes these extension tubes non-suitable for me. So, at least I know extension tubes are not an option for me, thanks to this TC. What's the focal length of the lens? The subject distance and the DOF are just the laws of physics. They apply to macro photography, no matter how you get to it. I have a 60 macro lens. At 1:1 magnification, the subject is about 2" from the front of the lens. A 100mm macro lens, also at 1:1 magnification, gives me about 9" from the front of the lens to the subject. Roughly, to get to 1:1 magnification, you need to bring the lens out from the camera body a distance as great as the focal length of the lens. So to get to 1:1, a 60mm lens needs 60mm tube and a 100mm lens needs 100mm tube. An 18mm lens needs only 18mm tube to get to 1:1. But the subject practically touches the lens. For setup with extension tube, the focusing mechanism on the lens doesn't do a whole lot. It's easier to move the whole setup back and forth. A macro focusing rail on a tripod is of great help. DOF is always a problem. When you close down the aperture to get decent DOF, you don't have enough light. That's why you also need a flash, preferrably one with variable output.

03-04-2009, 06:05 AM	#10
pcarfan Veteran Member Join Date: Sep 2007 Location: Dayton, Ohio Photos: Gallery \| Albums Posts: 2,978 Original Poster	It's a 50mm lens. It's a 1:2 macro. Does this native magnification matter on what a 25mm long extension tube would do ? so what is the final magnification on a 50mm 1:2 macro with a 25mm extension tube ? Thanks P.S: I know about the dof being razor thin even before, never the less, it is just amazing to see it first hand. I was trying it from f2.8 all the way to f16 (max), and was fine at f16, but I am not interested in using this particular lens anything other than F2.8 or F4...I am just working on all possible use for this lens with it's quirkiness.

03-04-2009, 01:27 PM	#11
roentarre Veteran Member Join Date: Oct 2006 Location: Melbourne, Australia Posts: 11,783	Moved to accessory section.

03-04-2009, 02:20 PM	#12
SOldBear Veteran Member Join Date: Feb 2009 Location: Alameda, CA Posts: 3,206	Originally posted by pcarfan It's a 50mm lens. It's a 1:2 macro. Does this native magnification matter on what a 25mm long extension tube would do ? so what is the final magnification on a 50mm 1:2 macro with a 25mm extension tube ? I apologize if I ask wrong questions here.... Are you sure the 50mm is a macro lens capable of 1:2 magnification? If it is, adding a 25mm will bring the magnification to 1:1, or very close to that. What I'm afraid of is that the lens is a 50mm 1:2 lens. 1:2 here means f/2, the largest aperture, having nothing to do with macro. A macro lens in most cases will have the word "macro" somewhere on the lens. A macro lens will extend significantly at close focus. See photos below: Infinity focus: At 1:1 magnification: It does not matter how good the lens is, at macro range, F/2.8 - F/4.0 is not very practical.

03-04-2009, 02:54 PM	#13
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,891	your lens is apparently, at least, 1:2 macro, it is truely a macro lens based upon the photos you show with the extension of the group when focused close, I also like the apature scale showing the apparant apature change when you focus out, very useful for flash work. As for final magnification ratio, assuming lens is 1:2 yes 25 mm would probably take you to 1:1,

03-04-2009, 03:58 PM	#14
pcarfan Veteran Member Join Date: Sep 2007 Location: Dayton, Ohio Photos: Gallery \| Albums Posts: 2,978 Original Poster	It is a f2.8 1:2 macro lens, I am sure of it. It is the Volna-9. I know A-contacts are usually useless with M42 lenses, but I have a plan But, now I can see how this ext. tube would be useful to get close with certain subjects, so I will keep this frankenstein extender for such occasions.

03-04-2009, 04:15 PM	#15
SOldBear Veteran Member Join Date: Feb 2009 Location: Alameda, CA Posts: 3,206	Originally posted by pcarfan It is a f2.8 1:2 macro lens, I am sure of it.. Sorry for doubting you. On some forum here, someone asks whether the SMC Pentax-M 50mm 1:2 has 1:2 magnification.... With a 1:2 macro lens, the extension tube is still useful. Many macro lenses can go 1:2, and come with an extension tube to get to 1:1.

Can I convert a TC into an extension tube with A contacts

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