[cyberjunkie]

I thought I could find a single thread dedicated to lens conversions.
I couldn't find one.
There are some specific messages reporting about a successful lens conversion, and some even give details about the procedure, but there is no place where we can find different conversion projects. So I thought that it could be worth trying to check if there is any interest in this kind of projects, and if there are other people willing to share their successful attempt at converting lenses made for other systems (or originally meant for other use) to PK or M42 mount.
I don't think there should be any limit. Each and every working conversion can be taken as an example by other pentaxians willing to expand their lens stable, from a very easy replacement of the original bayonet with a Leitax one, to complex adaptations of projection lenses.
It would be very interesting to undersand WHY, and what kind of optical signature the adapted lens provides.

I start with two conversions of Meyer lenses with breech lock atachment, meant for Altix cameras with behind-the-lens leaf shutter.
One is the Trioplan 2.9/50mm, the other is the Primagon 4.5/35mm.
Both are bokeh monsters.
The Trioplan is known for its bubble bokeh, but of course the longer the focal the bigger the balloons
The Primagon is one of the few wide angles that have such a beautiful, exaggerated bokeh. Given the not-so-great MFD, for close subjects the use of a thin extension ring is a good idea...

I have no Dremel knock-off here, so I slowly removed with a file the three "wings" of the bayonet, almost completely. Just enough to slide in a M39-toM42 adapter ring.
I removed the mount from one of the lenses to avoid getting aluminum dust inside the lens. Bad idea, cause trying to remount it a ben two springs, and I had to remeddy with some ingenuity... and plenty of time. The next ime, I'll use a Dremel, and protect the lens with some tape.
Another error I made in my first attempt was to glue the ring before adding the PK bayonet (a cheap chinese M42-to-PK non-flanged adapter). If the two rings are glued together beforehand, for example with a couple of drops of cyanacrylic glue, it's much much easier to align the red dot of the PK adapter with the focusing and diaphragm references. At first i glued the inner ring with bi-component acrylic glue, and then i screwed in the PK adapter. Despite trying my best, the second adapter is slightly misaligned, if it's fully screwed in. If the two rings are screwed one into the other, so to get a flat surface, it's easy to slide the duo ino place, align the references, and at last glue the inner ring o the lens body.
As an alternative acrylic bi-component, it's possible to use simple magic glue (careful, the less the better), or acrylic grout for wet surfaces, the kind used to repair leaking pipes. I used the three different options in different attempts, and I found that magic glue allows for a very neat job, almost invisible, but is very very liquid, and spreads everywhere. Three super tiny drops are sufficient.
I wanted to seal the inner ring with black hot glue, to control light leaks, but if the inner ring is pushed flat against the rear base of the lens, with the two indents towards the camera, there are no light leaks at all.

This kind of conversion is very doable:
1) it can be done with super cheap adapters and with no specialistic tools.
2) if the inner (M39-to-M42) ring is firmly seated on the back of the lens, magically you get spot-on infinity! The reason is that the ring seats well beyond the bayonet... which explains why a much shorter registry, that on paper would never work with a DSLR, can be made compatible with our Pentax cameras. The adaptation of an Exakta mount, that is done exactly the same way, has a problem. Following he same procedure you won't get infinity. The mating surface should be worked at a lathe, or the helicoid adjusted.

I have already done, bu not finalized, the CZJ Tessar 2.8/50mm for Altix. Now I have just adapted the Primagon and the Trioplan. In the near future I will do the same to the Telefogar 90mm.
Two out of four lenses are impossible, or almost impossible, to find in M42 mount, and all of them are "bokeh specialists".

One caveat. When M42-to-PK non-flanged adapter rings are used with lenses that have a small diameter at the mount, the indents of the adapter let some light in.
I found soft, thick elastic ties meant for hair, that are very practical to use, and stop any light leak. I always have one in my bag.


Here are two pics of the Primotar.
I'm sorry I didn't document the steps of my work, just how the lens looks after the surgery.
Photos of the Trioplan will follow.

[Cerebum]

Interesting thread I won a converted Isco Göttingen 45mm on EBay. It was originally mounted on something like a coronet or an aretta but was modified to fit m42. It was used on a Sony mirrorless thanks to a helicoid and an adapter. I have ordered a 17-31mm helicoid, hopefully I should be able to find infinity using that. Once the lens arrives I will post some pictures.

[cyberjunkie]

Interesting thread I won a converted Isco Göttingen 45mm on EBay..
Once the lens arrives I will post some pictures.

Good.
I'm curious
It's not a common conversion.

cheers

Paolo

[swanlefitte]

Great idea for a thread. I spent alot of time trying to find stuff before.
So Here are my quick and dirty nikkor 105 ai and ais conversions.

Simply unscrew the mount. Make a template to find the screw holes. Take a flanged m42 adapter and line it up so your lens will face correctly. Drill your holes and file the sides down where it gets in the way of turning the aperture. Then file down the sides of the aperture part till its flush. I also added a shim cut from a frozen juice lid.

[Just1MoreDave]

My conversion works but is more of a cautionary tale than a how-to. I saw an eBay auction for the Vivitar 55mm f2.8 1:1 macro, a pretty good lens that comes in lots of mounts. The seller was one of those people who had no interest in the lens, so he didn't list the mount or show a photo. So no one bid except me and I got it for $10, in Canon FD mount. I don't know why third-party makers made it so difficult to change mounts. I hoped to unscrew all the FD stuff and a spacer tube, then tack on a K mount and a different spacer. No luck there - the FD mount stuff even affected the connection between the iris and aperture ring, so I had to make my own connection. The aperture ring therefore moves the blades between full open and full closed, but the markings are wrong. My K-mount was attached at the wrong registration distance, like the lens has a permanent short extension tube. The lens does work, but is not that easy to use, and only focuses to 5 feet or so. It would be OK for fixed-distance product macros. I suggest anyone interested in the lens just buy it in M42 or K-mount.

[Cerebum]

OK, I got the isco gottingen 45mm but it is a great disappointment! all he has done is take it off the camera and screw a 25mm-m42 adapter on the back. The thread on the 25mm section is very slightly too big, so it will not tighten. There are several bits of uneven length standing up on the back so the plate does not fit flush. This lens has two diaphragms, one of which was stuck. The one controlling the aperture was also sticking. When I freed one, the other snapped shut, rendering it inoperable. One of the pins stopping the plate from settling actually controls the second diaphragm. There was nothing in the way he had set it up that would have allowed it to open. The only reason he got any pictures is because the aperture blades were stuck. Saying that, I have to say it is pretty. The lens maximum focus distance is about 10cm so it is pretty useless for anything other than macro and I won't be using it for that because I have better lenses but it will make a rather nice paperweight

[cyberjunkie]

It's not a second diaphragm, it's the leaf (central) shutter. There should be a way to keep it open, thus making the lens usable at least at short distance.
It could have a nice bokeh shooting flowers...
Usually 45/50mm lenses set in a leaf shutter can't reach infinity, unless one can find a focusing helicoid large enough to fit the rear of the leans deep enough, with the rear glass slightly protruding inside the mirror box.
I advise anybody willing to tackle this kind of conversion, to choose optics with focal length > 80mm. In my experience a Trioplan 75mm in leaf shutter is still too short. You won't get infinity. I tried using a Schneider No.1 lens barrel, bu it makes no difference at all. No infinity, at least with a cheap M42 helicoid.
I didn't try with a larger helicoid (M65), but in this case a cup shaped adapter should be made (with a lathe).
I suggest to use projection lenses (around 85mm or more), or taking lenses in leaf shutter with a focal longer than 90/100mm.
Of course those shooting with a mirrorless don't have this kind of problems. The register is way shorter...

cheers

Paolo

[Cerebum]

It's not a second diaphragm, it's the leaf (central) shutter. There should be a way to keep it open, thus making the lens usable at least at short distance.
It could have a nice bokeh shooting flowers...
Usually 45/50mm lenses set in a leaf shutter can't reach infinity, unless one can find a focusing helicoid large enough to fit the rear of the leans deep enough, with the rear glass slightly protruding inside the mirror box.
I advise anybody willing to tackle this kind of conversion, to choose optics with focal length > 80mm. In my experience a Trioplan 75mm in leaf shutter is still too short. You won't get infinity. I tried using a Schneider No.1 lens barrel, bu it makes no difference at all. No infinity, at least with a cheap M42 helicoid.
I didn't try with a larger helicoid (M65), but in this case a cup shaped adapter should be made (with a lathe).
I suggest to use projection lenses (around 85mm or more), or taking lenses in leaf shutter with a focal longer than 90/100mm.
Of course those shooting with a mirrorless don't have this kind of problems. The register is way shorter...

cheers

Paolo

I did a quick fix with a bent paperclip you can see it in the pic. The close focus is staggering, you are nearly touching the subject. I may try a bit of extreme macro with it. The thing only cost £25 and is an interesting experiment however I did free lens without the mounting plate and with the rear lens virtually inside my K30 and focus was still short. It is a toy I will have fun with it

[JKoch]

Hi Pentax Owners.

Few days ago I bought old Sankyo Kohki Komura 135mm f 1:2,8 lens. The lens needs cleaning because mold and dust inside it. I wonder how the lens to mount in my Pentax K5 II. The lens has Minolta mounting, probably. Could someone suggest what adapter to use to convert it into Pentax K, please? Here are few pictures of the lens:

[JKoch]

I found adapter as showed below:


This is MD-PK adapter. At this moment I have poor knowledge about Minolta mounting standards. I need to search more deep in internet. But anyway I hope someone help me.

[cyberjunkie]

Few days ago I bought old Sankyo Kohki Komura 135mm f 1:2,8 lens. The lens needs cleaning because mold and dust inside it. I wonder how the lens to mount in my Pentax K5 II. The lens has Minolta mounting, probably. Could someone suggest what adapter to use to convert it into Pentax K, please? Here are few pictures of the lens:

Unless you have a friend who's mechanically gifted and owns a lathe (or at least a burr with micrometric setting), the only option is to buy another Sankyo Kohki lens that has a UNI adapter in M42 mount.
The first version of the UNI mount is not dissimilar from the T-mount, but it's not compatible.

If you are very handy, you can try to use a Dremel with a few accessories. First find the right register you need to obtain, remove some material from the rear of the UNI mount, do the same with the bayonet, drill three or four holes on the mount, and use little screws to secure a flanged PK adapter to the rear of the mount.
Remove the material slowly, tape the adapter, and see how far you are from correct infinity. Continue until infinity is spot on.
Could be worth the time and the effort, cause Komura lenses are quite good. Completing such complex project would be very rewarding...
I suggest to freelens first, and see if you like the signature of the optic.

The adapter you show is usable only for bellows, macro heads, or you are fine with using the lens only at close distance.
You won't get infinity, not even close!

cheers

Paolo

[cyberjunkie]

Here are three pictures shot with the Altix lenses I converted. Both optics were mounted on a short extension tube.

Meyer Primagon f/4.5 35mm wide open:



Meyer Trioplan f/2.9 50mm wide open



Meyer Trioplan f/2.9 50mm stopped down to f/5.6


Lovely bokeh. Even stopped down, and even using a 35mm...

[JKoch]

Thank you for your advice, Paolo.
I am not high experienced in lens mounting and adapters. At this moment, according your suggestion and bought other lenses with Pentax and Uni-Auto adapters. In last week I have bought two lenses:
- Komuranon type 821-S 80-210mm 1:4.5 with Pentax ME mount
- Sankyo Kohki Super-Komura 135mm 1:2.8 with Uni Auto mount.
Pictures of both mounts are below.

Using one or both of above mounts I hope to fit my basic Komura lens to Pentax body.
I will post more details after both above lenses I receive.

[cyberjunkie]

The UNI and the UNI AUTO are different.
The UNI adapter is for preset lenses

[JKoch]

My Sankyo Kohki Komura 135mm 1:2.8 with Minolta mount is preset model. What are differences between UNI and UNI AUTO mounts?