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10-19-2018, 07:38 AM   #1
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Should I get my hands dirty on this gem?? (wisdom needed)

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Hello everybody!
I recently got my hands on a Konica Hexanon 57/1.2 and I want to convert it into a Pentax K mount so bad!
there is a guide in the forum about this procedure performed on Konica AR mounts but not specifically on this lens.
I know in theory what I have to do:
the konica has a 40 mm flange distance while the pentax has a 45.46 mm one. so the whole block of the lens has to move inward 5.46 mm in relation to the mount to achieve infinity focus.
One of the problems is mirror clearance, the rear glass element is too far back and I am afraid it will hit the mirror. I read at the adaptist site that the k mount needs at least 9mm of clearance from the mount base to be safe.
The furthermorst point of the lens at the actual state is about 6mm from the mount base, If I add the flange compensation of 5.46 it will go 11.46 mm and it will definitely crrash with the mirror. But I noticed that I can remoove the base of the rear element and I might shave a couple of mm. I need some advice, I dont want to screw up this beautiful piece of a lens.
Here are some pictures of it:

http://=https://drive.google.com/file/d/1h3UzhAeTvF_sM9kml56xXU9l249ee52E/vi...- Google Drive
http://="https://drive.google.com/file/d/1PT8J9TCpFJZyHwWnModX0Dbu8gkyscaq/v...ew?usp=sharing
http://="https://drive.google.com/file/d/1VyZJlGIOqK1q5uM0CU9JHUNuT_2TXzP9/v...ew?usp=sharing

10-19-2018, 07:49 AM   #2
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The biggest issue is going to be trying to figure out where that 5+ mm has to come from.

There won't be that much travel allowed in the lens focusing helical adjustment to move the optics back that far.

If you machine that much metal off the back of the lens housing, and then put a K mount onto it, where's the aperture ring going to go?

I'm not saying it's impossible, it's just likely a lot, lot, lot harder than it looks.

I tried converting a nice Konica 200mm 3.5 to Nikon mount about 20 years ago. Using a mount scavenged from an old teleconverter, I got it all fitted up. Was quite proud of my work, but ended up realizing I couldn't move the optics back the necessary 5+ mm, even on a lens that big. Fortunately, I was able to put the Konica mount back on, and then found a Konica fan who took it off my hands.
10-19-2018, 08:07 AM   #3
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QuoteOriginally posted by Ontarian50 Quote
The biggest issue is going to be trying to figure out where that 5+ mm has to come from.

There won't be that much travel allowed in the lens focusing helical adjustment to move the optics back that far.

If you machine that much metal off the back of the lens housing, and then put a K mount onto it, where's the aperture ring going to go?

I'm not saying it's impossible, it's just likely a lot, lot, lot harder than it looks.

I tried converting a nice Konica 200mm 3.5 to Nikon mount about 20 years ago. Using a mount scavenged from an old teleconverter, I got it all fitted up. Was quite proud of my work, but ended up realizing I couldn't move the optics back the necessary 5+ mm, even on a lens that big. Fortunately, I was able to put the Konica mount back on, and then found a Konica fan who took it off my hands.
Nice point you are making there! For what I've noticed so far the aperture ring is elongated towards the back until it embraces the mount base. This is the only lens I've seen where there is no actual contact between the lens mount base and the body mount, in fact this is achieved bu the extension of the aperture ring. coincidentally, this extension is about 5mm long, just the right amount I need to achieve infinity focus. Now, of course there has to be some space or a brush between the mount and the aperture ring so they dont grind. But it is not the space on the outside that bothers me, it is on the inside. I have to study the spaces between the rings and triggers on the inside(if there are any). I think the helical is further down.
10-19-2018, 08:44 AM - 1 Like   #4
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Just get a Konica SLR and shoot with it. You have the lens. Now get the right camera for it. F/1.2 ist beautiful on film. I bet you'll be pleasantly surprised.



10-19-2018, 10:08 AM - 1 Like   #5
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QuoteOriginally posted by torashi Quote
Just get a Konica SLR and shoot with it. You have the lens. Now get the right camera for it. F/1.2 ist beautiful on film. I bet you'll be pleasantly surprised.
Or, a Sony a7/a9 body, with appropriate adapter.
10-19-2018, 12:16 PM   #6
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QuoteOriginally posted by shyrsio Quote
there is a guide in the forum about this procedure performed on Konica AR mounts but not specifically on this lens.
When I searched for the guide you mentioned, I could only find conversions where aftermarket lenses (Vivitar, etc) were changed over to K mount.

Those lenses were designed around a front end that was more or less universal, and the rear end was built to make it work on a specific mount - this means the actual mount, the flange distance, and the aperture linkage.

Shortening up the longer Konica rear end, and then putting K mount on it is certainly possible (although you obviously lose auto aperture) because there's "meat" to work with on the longer Konica rear.

Unfortunately, genuine Konica Hexanons aren't designed around a front/rear assembly system. Shortening up the whole shebang by more than five millimeters, especially on a short lens like a normal or wide angle is a real headache.
10-19-2018, 12:54 PM   #7
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QuoteOriginally posted by shyrsio Quote
Here are some pictures of it:
Your links are not working for me.

10-19-2018, 12:57 PM - 1 Like   #8
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I think I'd do a gentle CLA on your 57mm Konica, sell it, and find a lens that is easier to drag over to k-mount, or one that already has a k-mount on it. There are some 3rd party 55mm f1.2's from brands like Porst, Ricoh, Revue, and Cosina (who may or may not have actually made the lenses themselves...) that came in k-mount.

There's also the Leitax mount adaption hardware where you can find lenses that already have been adapted by Leitax for k-mount. Konica isn't listed, so again, it'd be sell-on time for the lens you're holding now.
10-19-2018, 06:11 PM   #9
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QuoteOriginally posted by shyrsio Quote
Hello everybody!
I recently got my hands on a Konica Hexanon 57/1.2 and I want to convert it into a Pentax K mount so bad!
there is a guide in the forum about this procedure performed on Konica AR mounts but not specifically on this lens.
I know in theory what I have to do:
the konica has a 40 mm flange distance while the pentax has a 45.46 mm one. so the whole block of the lens has to move inward 5.46 mm in relation to the mount to achieve infinity focus.
One of the problems is mirror clearance, the rear glass element is too far back and I am afraid it will hit the mirror. I read at the adaptist site that the k mount needs at least 9mm of clearance from the mount base to be safe.
The furthermorst point of the lens at the actual state is about 6mm from the mount base, If I add the flange compensation of 5.46 it will go 11.46 mm and it will definitely crrash with the mirror. But I noticed that I can remoove the base of the rear element and I might shave a couple of mm. I need some advice, I dont want to screw up this beautiful piece of a lens.
Here are some pictures of it:

http://=https://drive.google.com/file/d/1h3UzhAeTvF_sM9kml56xXU9l249ee52E/vi...- Google Drive
http://="https://drive.google.com/file/d/1PT8J9TCpFJZyHwWnModX0Dbu8gkyscaq/v...ew?usp=sharing
http://="https://drive.google.com/file/d/1VyZJlGIOqK1q5uM0CU9JHUNuT_2TXzP9/v...ew?usp=sharing
You would do better to forgo surgery on the lens and pick up a mirrorless of some sort and get an adapter.
10-20-2018, 04:19 AM - 1 Like   #10
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QuoteOriginally posted by Wheatfield Quote
You would do better to forgo surgery on the lens and pick up a mirrorless of some sort and get an adapter.
What he said. There are lots of used Sony cameras on the market and the list of available adapters is long.

The surgery required for K mount compatibility would utterly destroy any value of what must be a very rare lens.

Or you could get a Samsung NX - recently deceased camera (brand) with a long dead lens mount. I like the idea.
10-21-2018, 06:13 AM   #11
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Thank you for the replies!
I managed to open it a bit from behind and i reckon the task is indeed difficult. on the other hand i think this lens would be better used on FF. i guess I will put it on sale.
12-12-2018, 08:51 AM   #12
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.... and in sale it goes: KONICA HEXANON 57mm F/1.2 in good condition | eBay

I am so sorry to let go of this beautiful creature, but i have to finance my acquisition of a K3 ii. so if any of you are interested take a look. Thanks!
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