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04-01-2012, 01:02 PM   #1
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Can I modify to PK ... a CZJ Prakticar 1.4/50 MC ?

Bonjour,

There was a photo fair/swap meet today at Montamisé (near Poitiers), and I picked up the above lens on a whim ... got it cheap with a "Helios-44M 2/58" in M42 that I was really interested in ... I know nothing about this CZJ lens and it seems to have a "B" or "PB" mount from the photos that I have seen on Google Images.

I chanced upon an old thread saying that this lens cannot be modified to PK, etc. Is that correct? Any advice would be greatly appreciated.

Again, I got this cheap and the blades are oily and sticky, but the glass is good ... there's a converter to 4/3 format, so maybe I use it there someday in the future ... as the French say, "Merci d'avance" for any input and/or assistance.

Allez et salut, John le Frog



Last edited by Jean Poitiers; 04-03-2012 at 10:03 AM.
04-01-2012, 01:24 PM   #2
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There was a thread about this last year.

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/153836-praktic...x-k-mount.html
04-01-2012, 01:33 PM   #3
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Merci ...

QuoteOriginally posted by boriscleto Quote

Bonsoir,

Thanks, I don't think that I saw that one ... will read soon. Does it have a happy ending?

Salut, J
04-01-2012, 01:58 PM   #4
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Here is some additional information. It appears that it can be done....
Also, I am guessing that Rico has had some experience on the mount...



04-01-2012, 02:14 PM   #5
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C'est super !

Bonsoir interested_observer,

Thanks a lot ... and I also thought about just PM'ing Rico directly about this question.

Merci encore et salut, J Frog
04-01-2012, 04:56 PM   #6
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QuoteOriginally posted by John Poitiers Quote
I also thought about just PM'ing Rico directly about this question.
I have one PB lens, a Pentacon (Meyer) Prakticar MC 50/2.4, on which I started work but hit a dead-end. I will check these links to guide my further efforts after I return to my home base in a few weeks. Thanks!
04-02-2012, 11:39 AM   #7
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QuoteOriginally posted by interested_observer Quote
DIY PK-mount Carl Zeiss Jena Pancolar 50/1.8
That thread was one of mine and had a moderately happy ending, but there was a point at which the conversion changed from non-destructive to destructive in order to get infinity focus (although the destruction is limited to bending the diaphragm linkage, so would probably be reversible by a skilled technician).

As the 50/1.4 is comparatively rare, sought after and comparatively valuable (the donor lens in my conversion was under 10GBP), I'd suggest getting it serviced and using it with micro 4/3 if that is an option. Whilst it may be possible to convert it to PK mount, from my experience on the 50/1.8, it is likely to be challenging to get anywhere near infinity focus (unless, of course, you have metal fabrication skills!).

04-02-2012, 01:42 PM   #8
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Merci Monsieur Rico ...

QuoteOriginally posted by RioRico Quote
I have one PB lens, a Pentacon (Meyer) Prakticar MC 50/2.4, on which I started work but hit a dead-end. I will check these links to guide my further efforts after I return to my home base in a few weeks. Thanks!
Thanks a lot and there's no rush whatsoever ... Salut, J
04-02-2012, 01:47 PM   #9
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4/3 possible ...

QuoteOriginally posted by sorted78 Quote
... I'd suggest getting it serviced and using it with micro 4/3 if that is an option.

... it is likely to be challenging to get anywhere near infinity focus.
Bonjour sorted78,

Thanks for your input and if it's too difficult then I did think about servicing the lens and using it with another system ... 4/3 not out of the question.

As for infinity focus, I'd almost give that up, if push comes to shove ...

Merci encore et salut, J Frog
04-02-2012, 01:50 PM   #10
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Photos of lens and PB(?) mount, etc

Bonjour,

For those who may be curious, here are some photos ... A+, J

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Last edited by Jean Poitiers; 04-03-2012 at 10:06 AM.
04-02-2012, 01:56 PM   #11
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The registration distance is somewhat shorter for the Praktica B mount than for K (and m42), which mean that you need to do some surgery, to remove a bit of the lens to shorten the registration distance. Doing that the risk is that the rear lens element gets to close to the mirror. Many other problems can occur of course.
However, many of the lenses available in Praktica B mount are directly related to earlier Praktica m42 lenses, and since m42 and K share the same registration distance, it should mean that the rear lens element to sensor/film should still have the same distance as it m42 ancestor had, once you have shaved of the difference in registration distance.
04-03-2012, 01:15 PM   #12
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QuoteOriginally posted by John Poitiers Quote
As for infinity focus, I'd almost give that up, if push comes to shove ...
That is a fair point; I did experiment a bit and would have been prepared to give up infinity, however, I found that I couldn't focus beyond 3-4 feet using the thinnest PK mount I could find and adjusting the focus helicoid alone before the extended helicoid fouled the diaphragm linkage. As I wanted to be able to focus a bit further away, I resorted to removing/modifying the components of the diaphragm mechanism that prevented the helicoid moving further back towards the mount. .

As the focus scale is non-linear, the difference in physical extension between being able to focus a useful distance away and all the way to infinity was well under 1mm, so seemed worth a bit more tweaking to accommodate.

I'd be interested if you do decide to modify it (not least because I'd like a Prakticar 50/1.4 as well) and will happily do a more detailed writeup of my 50/1.8 mods if that's of any interest.
04-03-2012, 11:15 PM   #13
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Oui et merci d'avance ...

QuoteOriginally posted by sorted78 Quote
... I'd be interested if you do decide to modify it (not least because I'd like a Prakticar 50/1.4 as well) and will happily do a more detailed writeup of my 50/1.8 mods if that's of any interest.

Bonjour
sorted78,

Thanks a lot for your input and experiences ... always appreciated and good to know as much as possible. And yes, I would be interested in a more detailed write up on your modification experience.

I think that I am going to remove the back mount just the get an idea of what to do thereafter ... kind of a per-modification recognizance step. I will document as well and maybe a lens article can be put together at a later date, if and/or after my modification, etc..

Again, merci beaucoup et salut, John le Frog
05-09-2012, 02:07 PM   #14
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Bonjour RioRico (encore) ...

QuoteOriginally posted by RioRico Quote
I have one PB lens, a Pentacon (Meyer) Prakticar MC 50/2.4, on which I started work but hit a dead-end. I will check these links to guide my further efforts after I return to my home base in a few weeks. Thanks!
Salut encore,

Again, I do not want to pester you, but what do you think about a possible modification here? If it's too much trouble, let it go ... I could resell this lens for a lot more than I purchased it for ... still, it's "curiousity that kill the cat" symdrome here ... Allez et à plus tard.

Bien cordialement, John "the former Okie now (happily) stuck in France" ...
05-09-2012, 07:57 PM   #15
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QuoteOriginally posted by Jean Poitiers Quote
QuoteOriginally posted by RioRico:
I have one PB lens, a Pentacon (Meyer) Prakticar MC 50/2.4, on which I started work but hit a dead-end. I will check these links to guide my further efforts after I return to my home base in a few weeks.
Again, I do not want to pester you, but what do you think about a possible modification here? If it's too much trouble, let it go ... I could resell this lens for a lot more than I purchased it for ... still, it's "curiousity that kill the cat" symdrome here
Well, I'm back in my California home again, and I haven't yet had a chance to diddle the Prakticar. I think the mod may be more trouble than it's worth, but I'll try it. For you, I'll suggest that you TAKE THE MONEY AND RUN! Maybe experiment with a cheap lens. Good luck!

Last edited by RioRico; 05-09-2012 at 08:13 PM.
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