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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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08-04-2011, 12:48 AM   #31
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I converted a Tokina 24-40 from OM to PK mount

I had the hypothesis that since Tokina was building lenses for many brands the elements must be common; and thus the mounts should be interchangeable without much trouble.

Results are fine, as you can see; however the spring that holds the diaphragm must be switched to the other side.... winter project!!!

08-04-2011, 01:51 AM   #32
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Oh no, now I'll have to start looking for Rokkors and Hexanons...
07-10-2012, 05:15 AM   #33
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Hi, I would like to convert the same Vivitar 70-210 to Pentax K, in order to use it on my K20D. But the Vivitar is Nikon mount. Is the process the same ? I don't know the flange focal distance of Nikon system. Could you help ?

Thanks
A Guy called Guy from old Orleans (France)
07-11-2012, 11:01 AM   #34
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i'd like to know if someone ever converted the Konica 40mm f1.8 to Pentax ?

this seems tricky considering the size of the lens ...


Last edited by aurele; 07-11-2012 at 11:09 AM.
07-11-2012, 11:02 AM   #35
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QuoteOriginally posted by Deeco Quote
Hi, I would like to convert the same Vivitar 70-210 to Pentax K, in order to use it on my K20D. But the Vivitar is Nikon mount. Is the process the same ? I don't know the flange focal distance of Nikon system. Could you help ?

Thanks
A Guy called Guy from old Orleans (France)
the flange distance should be the same or almost. try to find a mount that do the same thickness of the current Nikon mount of the lens.
07-11-2012, 12:16 PM   #36
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Well, I finally found here : Nikon F-mount - Wikipedia, the free encyclopedia
FFd ok Nikon F mount is 46,5mm.
07-14-2012, 10:27 AM   #37
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Welllll
vivitar used to make lenses for many cameras so chances are the mount is a modifiable universal one like the one from Tokina
I will look into my 70-210 (pentax S) and see inside.



QuoteOriginally posted by Deeco Quote
Hi, I would like to convert the same Vivitar 70-210 to Pentax K, in order to use it on my K20D. But the Vivitar is Nikon mount. Is the process the same ? I don't know the flange focal distance of Nikon system. Could you help ?

Thanks
A Guy called Guy from old Orleans (France)
07-15-2012, 04:11 AM   #38
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Ok, I'm interested to know details !

08-22-2012, 12:24 PM   #39
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Has anyone done a conversion of the Mamiya E mount (for their 35mm Z series bodies ) to Pentax K. The flange focal distances are fairly close - 45.5 for the E vs 45.46 for the K.
10-25-2012, 10:47 PM   #40
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QuoteOriginally posted by vietlh81 Quote
1 - Minolta Rokkor 58mm f/1.2 conversion

Guide to converting the legendary Minolta Rokkor PG 58mm f/1.2
1) Introduction
The Minolta MC/MD register distance is about 43.72mm, whereas the Pentax one is 45.46mm. The difference between them is about 1.74mm.

Required things:
- A M42-PK adapter (~7$)
- Some screwdrivers with small diameter.
- A drilling machine with 2 drills: 2mm and 3mm.
- A file.

2)Disassembling the mount

There are 8 screws, we need to unscrew the 4 long ones, because the 4 short ones hold the diaphragm actuator with the mount.

File off the ridge around the outside of the aperture ring.
In this above photo, the ridge were cut off.

Continue to unscrew the 4 screws of black ring.

Rotate the aluminum ring in counterclockwise direction. Because we don't need the mount spacer which have a thickness 4mm. Therefore we must adjust 4 - 1.74 = 2.26mm in height by rotating the ring.


3)Reassembling the new mount:
After rotating, we re-screw the black ring.
Drill the 4 holes respectively on the M42-PK adapter.
Note that: the red dot on the adapter will the same position with the diamond shape

Place the aperture ring in its position with the ball ring. Beware of the ball ring. It is very small, Do not lost it.

Re-screw 4 long screws on the new PK mount.

Voilą, the conversion is done.


We can do the same way with Minolta Rokkor-X 50mm f/1.2. This is the later version with MD mount. This lens has not the spacer mount, therefore we must file the lens cover as the image.


I converted the Kiron 28mm f/2 as the same way of the Rokkor-X 50mm. Its focal length is smaller, so it needed to file more precisely in order to focus to the infinity.

Here some results of Kiron 28mm with infinity focus:

and close focusing:
Whenever people convert this for a Canon full frame they apparently need to file rear element metal hood just so it barely clears the mirror of the 5d. Given that the Canon flange distance is 44 and pentax 45.5 would such conversion be possibly used on a pentax old film camera that has a full frame? (Assuming without sacraficing infinity focus).
01-20-2013, 10:50 AM   #41
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I have a Minolta Rokkor 50mm f1.4 that I was planning to subject to surgery along prescribed lines. Then I realized that MD-PK adapters are readily available. My understanding is that a (cheap, glass-less) MD-PK adapter won't permit infinity focus.But I only intend using this lens for portraits, Will the adapter be likely good enough for portrait use or will all images regardless of distance from camera remain out of focus? This is a fascinating thread, which I don't wish to contaminate with a basic question...but the answer might help laymen (like me) from prematurely butchering lenses :-)
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