Konica, Minolta, etc. mount to Pentax K - How to save the old lenses

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.

Voilà, 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.

[vietlh81]

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.

Voilà, 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:

Click on the image to view it in a larger size

and close focusing:

[Adam]

Thanks very much for the contribution. Article approved!

[Alonsozjj]

That's a great job!

[vietlh81]

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.