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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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04-04-2009, 09:00 AM - 4 Likes   #2
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Minolta MC/MD mount to Pentax K

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:

Last edited by vietlh81; 04-04-2009 at 09:39 AM.
04-04-2009, 11:58 AM   #3
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Thanks very much for the contribution. Article approved!

Adam
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04-20-2009, 08:02 AM   #4
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That's a great job!

09-18-2009, 11:46 PM - 1 Like   #5
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Thanks for your appreciations. I've recently received the legendary Vivitar 100mm f2.8 (Kiron 105mm f2.5) for Minolta MD mount. So I intended to convert it to Pentax K mount to take the macro photos.



The conversion to Pentax K mount is quite easy, but comparing to the last conversion, this one has the Auto Aperture function. I observed that the Minolta MD mount is nearly the same with Pentax K's one. Therefore, this time, I put the diaphragm actuator in the location as the other Pentax K lens (as the image below).

Combining with the Pentax K-M to KA conversion, finally I have a Vivitar KA 100mm f2.8

Here some results on my K100D:



@f22 & f32: the photos are a underexposured, but with a flash, this won't be important.

Here is a sample of macro photo with flash at f/11:
.

Thanks for your reading.
01-05-2010, 04:14 PM   #6
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Minolta MD Rokkor X -->pentax K Sucess

Thanks for the inspiring thread.

I have had a little fun this week, in scouting the local camera shop the used shelf had a lovely Rokkor 50 f1.7 lens. these have a legendary reputation (do a search on flikr).

I weekend and $25 later i had the seeds of a great project. a little browsing through my obsolete junk box turned up a genuine Pentax m42-k adapter.

To make a long story short I now have a fully functional 50mm 1.7 that the camera thinks is a Pentax A lens. All the metering modes work etc. In addition to doing the mechanical mount change, I also did the electrical interface, so this lens is now treated like a "native" Pentax lens.

I have attached a test shot done with existing (crappy) light indoors under florescent lights. I will do some more formal testing, and report back. meanwhile the image quality is fantastic.

Art

PS the shot was wide open f1.7 1/20 second - no post processing
Attached Images
 
01-05-2010, 04:43 PM   #7
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This is an inspiring and truly nerdy thread.
01-11-2010, 11:06 AM   #8
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Art (right, from Art Rutledge?), that is a truly inspiring shot.
I'm very curious to see your step by step and/or hear how this conversion went.
Thanks for sharing your work with us!

01-11-2010, 06:59 PM   #9
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We could use more articles like this over at Manual Focus Forum Are you by chance a member over there?
01-11-2010, 07:41 PM   #10
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No I am not a member (yet) I had planned to do a more formal work up and document it, but travel plans have interfered at this point. I depart for Australia (from Canada) tomorrow morning for 3 months. I can do so when I get back. I do have an extensive colection of CNC and manual machining equipment (lathes (manual) 3 and 4 axis mills) so it does make it rather easier to reproduce the result.

I am curious as to what the general opinion is for the next conversion? I have been looking over some of the nikkor macro lenses, as well as the pentax M to A conversions (a snap) The olympus lenses look to be a good candidate, but i havent identified any with an exceptional reputation, and after all that is the objective here to capture and reuse some of these orphaned stellar lenses.

Art
01-13-2010, 09:49 PM   #11
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Nice article! Which M42 adapter did you use? They seem to come in many different flange widths. I was hoping to convert a Vivitar 28 f2 Konica mount but after disassembling it there's no extra length to remove. I can probably gain 2 mm between the mount and some spacers but that's it. I may try it anyway. I had to take it apart anyway to get the oil off the aperture blades.
02-01-2010, 02:03 PM   #12
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@artrutledge: very nice work. Could you post some images of your conversion? I found a little difficult for converting Minolta 50 1.2 to Pentax KA mount because the diaphragm actuator is attached to the mount.

@slick100D: I use the alum adapter (black) for the lenses that have shorter focal length (kiron 28, Minolta 50).
For the longer focal length (Vivitar), I use the brass adapters (silver color) which are more solid and thicker. I think it is very difficult to convert the Vivitar 28 Konica because your lens has a very short focal length whereas the difference of distance flange between Pentax and Konica is not small at all (~5mm).
02-15-2010, 06:01 AM   #13
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Konica Autoflex / Miranda to Pentax Kx project

I have an offer to buy 2 old cameras and 5 lenses cheap and it seems at least possibe to adapt them for use on my K-x. Here is a very poor image of the stuff ( trying to make her take some better ones).



Here is te important thing. I do have an old Vivitar 80-200 (pictures under here) that doesnt work to well but the mount is fitted for use on my K-x. I am wiling to use that Vivitar for parts if thats of any use? I have a Dremel and tools so with instructions I should be able to do the job. Im especially interested in the unspecified tele zoom thats in the image but also the other 2 extra lenses. The data I have on the zoom are these: Expert auto tele converter 2x lins. Auto vivitar telephoto 200mm 1:3.5 Any input is welcome

Last edited by aliasant; 02-19-2013 at 10:21 AM.
02-18-2010, 02:11 PM   #14
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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.
02-18-2010, 09:18 PM   #15
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QuoteOriginally posted by vietlh81 Quote
@slick100D: I use the alum adapter (black) for the lenses that have shorter focal length (kiron 28, Minolta 50).
For the longer focal length (Vivitar), I use the brass adapters (silver color) which are more solid and thicker. I think it is very difficult to convert the Vivitar 28 Konica because your lens has a very short focal length whereas the difference of distance flange between Pentax and Konica is not small at all (~5mm).
Lowell Goudge showed me how to disconnect the focus ring from the focus helix. The Kiron Vivitars apparently have a large focusing range to accommodate different mounts and I was able to get infinity focus without any other modifications. It would be interesting to find out what other manufacturers also used this technique.

In addition, because I knew the lens could focus closer, I removed some of the focus ring skirt that acts as the focus stops. This gives me nearly 360 degrees of range. I'm considering removing the stop completely, but haven't yet.
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