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Konica, Minolta, etc. mount to Pentax K - How to save the old lenses
Posted By: vietlh81, 04-04-2009, 08:14 AM

Following the requests of Hin and OregonJim, I create a new topic on the lens conversion to PK mount. Hope it will be useful for the others who interest the lenses conversion. If it is not convenient in this section, mod or admin, please, move it to the convenient place.

1) Introduction

Following Marks Robert, the Vivitar 70-210 S1, version 3 is the best among three versions. The mine is KONICA mount, I decided to convert it to Pentax K mount.

The flange focal distance of Konica system is about 40,5mm, whereas the Pentax one is 45.5mm. Therefore, we must shave the lens about 5mm in order to focus to the infinity.

Here is the image of the lens before the conversion (sorry, because it from the seller)

Required things:
- A M42-PK adapter ~ 6$ (I bought from a seller on ebay)
- Some small screwdrivers
- A ruler
- A saw (A lathe will be better)
- A file
- A drilling machine with 2 drills: 2mm and 2.5mm

This conversion simply consists of two steps. Firstly, cut off 5mm and secondly replace the Konica mount by the M42-PK adapter.

2) Disassembling the lens and cutting away 5mm

Unscrew 4 cross-screws from the bottom of the lens to take out the Konica mount.

The M42-PK adapter is thinner than the Konica mount about 1mm. Therefore we must shave the other parts of the lens about 4mm.

This ring is associated with the aperture system of the lens by the trigger. I decided to shave the aluminum ring. Firstly, I sawed this ring, cut away 4mm. This ring screws on other part of the lens which has the thread as the image shown.


Secondly, I also sawed this part about 4mm as the below image. After that, I filed them, it would be better if I had a lathe instead of sawing.


The trigger were also cut away about 4mm in order to function correctly.
3) Drilling the mount and reassembling.

The Konica mount is totally inside the aperture ring. Therefore, we must shave the aperture ring in order to place the M42-PK adapter above. If not, 1mm economized from the difference between two mounts is useless.

Throw away the ring with red dot (the thickness of this ring is about 5mm)

Drill 4 holes respectively on the M42-PK mount. Re-screw 4 cross-screws with 4 new holes.

Voilą, the conversion is done.

Here are the results of the quick test.

IMHO, its colors are beautiful.

I have not yet converted to Pentax KA. I think it is more difficult and it needs more precise tool to convert.

Last edited by vietlh81; 04-04-2009 at 09:05 AM.
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02-19-2010, 02:28 AM   #16
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QuoteOriginally posted by vietlh81 Quote
Hi aliasant,
I am sorry for the late reply, because of my thesis.
If you intend to convert your lens to Pentax K, I think there are no problem. Just try to throw away 5mm of your lens. There exists another version of the Komine 200 3.5 for Pentax. Therefore, I am quite sure this will be successful.

But if you try to convert your lens to KA, I think it will be harder, because the distance of the actuator's movement of Konica is longer than the Pentax's one.
If you have some images of the mounts, it will be better.
Hope to help.
No worries. Replied to that pm.

11-18-2010, 11:26 PM   #17
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This is a great thread, I just brought a MD Rokkor 50mm 1:1.7 and was looking for adapters but the lens only cost me $10 and for the price of a adapter I could actually buy a 50mm that has a Pk mount, now this has given me a project for the weekend, thanks.
12-12-2010, 01:45 AM   #18
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wow i never thought to do this thank you for the guide this is awsome...
12-12-2010, 12:25 PM   #19
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I dearly wish I could do this but there is no way. I just don't have the right skills when it comes to this kind of thing and I don't know the tools you'd have to use well enough to risk it. There are lenses in my Yashica kit that I'd just love to have for my Pentax cameras. I think you should try that next, Art. Some of the Yashica lenses are really nice and IMHO deserve to be converted.

12-16-2010, 02:43 PM   #20
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any one know how to turn a minolta md mount in to a k mount or if it is simular to the instructions at the begining of this thread let me know thank you
12-16-2010, 11:41 PM   #21
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I did it, it was easy considering its only a 50mm lens but the results are beyond my expectations .
12-17-2010, 08:52 AM   #22
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I have a nice old manual f1.8 Minolta lens I'd like to use on my Pentax.

Isn't there a way to do this without physical modification?

Could I find a Minolta to M42 adapter, then get an M42 to K-mount adapter? Or would stacking two adapters affect focus?

Or what about putting a teleconverter between the two, would that work?
12-17-2010, 11:57 PM   #23
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You can buy adapters to convert from a minolta to a Pentax mount, but I have done no research to see what effects it may have. I'd expect there would be something that you would have to compromise to use it.
Do a search on this site or the web, bound to be a pro/con list with these adapters.

I found that it was a very basic operation to achive but if you have doubts, Don't.

Try ebay for the adapter, it's the first place I looked and found what I was looking for, it was just easier for me this way than the other.

Goodluck.

12-23-2010, 02:18 PM   #24
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Ok, here's the thing (i'm just gonna go with what I've read).
On wikidedia, it's listed

Minolta MD 43.50 mm
Pentax K mount 45.46 mm

The difference is only about 2mm (not 5 like some have stated)... but Wikipedia could be wrong lol. At any rate, let's just assume that it's 2mm (for the shake of the argument). That extra 2mm is not allowing you to focus to infinity... so the key here is to shave that suckka off.

Because the MD mount has a "spacer" in some of the lens (for example on here is those 50mm), you just save that suckka off and attach the K mount on (you get it from ebay for 6-7 bucks). and walla, it acts like a Pentax M.

Ok, so what if you shave off more then needed? then you won't be able to focus as close (so let say if you've done it right, the nearest you can focus if .5m, if you over shave it, then the closest you can focus is like 2m or 5m ect...).

One of the easiest way to do this, simply take off the old mount and slap on the new one, see how far you can focus, if it's not far enough, start shaving that spacer.
02-01-2011, 11:54 AM   #25
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any one ever try an olympus om to pentax k mount if you have and have any advice please let me know thankyou
03-01-2011, 05:21 PM   #26
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QuoteOriginally posted by clockwork247 Quote
Ok, here's the thing (i'm just gonna go with what I've read).
On wikidedia, it's listed

Minolta MD 43.50 mm
Pentax K mount 45.46 mm

The difference is only about 2mm (not 5 like some have stated)... but Wikipedia could be wrong lol. At any rate, let's just assume that it's 2mm (for the shake of the argument). That extra 2mm is not allowing you to focus to infinity... so the key here is to shave that suckka off.

Because the MD mount has a "spacer" in some of the lens (for example on here is those 50mm), you just save that suckka off and attach the K mount on (you get it from ebay for 6-7 bucks). and walla, it acts like a Pentax M.

Ok, so what if you shave off more then needed? then you won't be able to focus as close (so let say if you've done it right, the nearest you can focus if .5m, if you over shave it, then the closest you can focus is like 2m or 5m ect...).

One of the easiest way to do this, simply take off the old mount and slap on the new one, see how far you can focus, if it's not far enough, start shaving that spacer.
The thing I'm finding is that all the Minolta lenses are constructed differently. I have a 50mm f2 Rokkor and 50mm f1.2 (not Rokkor) I bought in the 1980s, and a very old 35mm f2.8 and 135mm f2.8 my grandfather gave me long ago. I also have other Minolta lenses like a 300mm f4.5 from the 80s. They all have entirely different mount constructions and lens constructions so the process for one is not the process for all. I don't have access to the right tools (a metal file is about it!) at this point so conversion is looking hopeless. I was able to bore out an M42 to K adapter to slide over the 50mm f2 lens mount attach and it produces decent macro shots but I need a lathe to grind away a lip that's about 1.5-2mm.

Attached is an example of a macro shot taken with the Minolta 50mm f2 lens of a fig leaf bud, I believe it's at f2, 1/80 sec.

Camera body is the K-r (brand new! Woo hoo!).
Attached Images
 

Last edited by piledon; 03-01-2011 at 06:40 PM. Reason: i.d. camera body
03-18-2011, 02:36 PM   #27
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Actually it does seem that closer to 5mm is required to be removed than 2mm. On some mounts that's going to be easier to achieve, like on my 50mm f1.2 (this was shown on what appears to be a very similar 50mm f1.2 Rokkor-x mount in a previous post by vietlh81) and 300mm f4.5. The others appear to be hopeless. Hopefully I'll get time to do it and will post pix if successful (and maybe if not successful; failures can be fascinating...especially if they include severe damage!).
04-05-2011, 01:07 PM   #28
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Ultimately I made the change with the 135mm f2.8 lens. I didn't do as nice a job as the one above where vietlh81 had the right screws. I used J-B Weld epoxy instead, and roughed up the surfaces to ensure a strong bond. It's imperfect (focuses beyond infinity) but I'll experiment with introducing a 0.8mm spacer which should make it closer to correct. You can see the lens and sample photos starting here and hitting "next".
08-03-2011, 11:27 AM   #29
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I just ran across this thread and I'm intrigued, just what I need another project. ;-)

So, most of the donor lenses mentioned here require material/parts to be removed, moving the rear lens element deeper into the body. It looks like the Canon R/FL/FD have a 42mm flange distance.

What is the opinion of those of you that have modified the Vivitar/Kiron to Pentax on doing the same with a lens originally with Canon FD?

Has anyone tried simply changing the bayonet on a lens originally with Olympus OM? This has a flange distance of 46mm, so an ~0.5mm shim would be needed under the PK bayonet ring...

Some interesting sites I found with flange to focal plane distance:
in order of distance, small to large
Camera Mounts Sorted by Register
Check out the links on that page to the list in alphabetical order and to the site he credits the original data to.

Another site to check out with a good discussion of mounts and a portrait catalog of different mounts
SLR Lens Mount Identification Guide

Cheers,
PT
08-03-2011, 01:20 PM   #30
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QuoteOriginally posted by Popeye.Tom Quote
What is the opinion of those of you that have modified the Vivitar/Kiron to Pentax on doing the same with a lens originally with Canon FD?
I've modded a number of lenses, but no Canon FD's. Instead, I sold those for a good profit, and bought some more usable glass.

QuoteQuote:
Has anyone tried simply changing the bayonet on a lens originally with Olympus OM? This has a flange distance of 46mm, so an ~0.5mm shim would be needed under the PK bayonet ring...
I've modded a number of OM and C/Y mount lenses for PK. I need only whip out the Dremel and shave away a little from their bayonet flags, so they'll fit under the PK mount lugs. Taper the flags about 10mm, that's all. For security, cut a slot in the lens base that's 1mm wide and deep and 6mm long, for the PK locking pin to engage. The half-mm register difference is inconsequential.
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