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09-15-2012, 01:53 AM   #1
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Jupiter-9 tweaking minimum focal distance

Hello,

I am looking for help on changing the MFD on a Jupiter-9.


I read somewhere, and of course I can't find it, that you can alter the MFD and have a J9 focus to about 50cm.


I did find an online guide on how to disassemble a J9 (see link).

http://allphotolenses.com/public/files/pdfs/0209e046cf1b8a29a4af9f50899ffab4.pdf

And there is a "focus limit" screw. However, my lens does not look the same as the lens that he is disassembling. Also, I don't believe that the screw that he is referring to is for MFD. It looks like it's for infinity focus.


Any help as to how to do this would be greatly appreciated.


Thanks you!

09-15-2012, 01:58 AM   #2
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There are quite a few versions of the Jupiter-9, it is hard to help without knowing exactly which one you have.
09-15-2012, 08:14 AM   #3
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You might get a little more traction on the Russian lens club thread, though here is not a bad place either. As mentioned above, there are several versions of the J-9 depending on target platform (M42, M39 (Zenit), M39 (LTM), Contax/Kiev, etc.) and construction varies. The PDF you linked to appears to be for the M39 (LTM) version which has a complex system of multiple helicoids to drive the rangefinder cam and focus mechanism. If you have the M42 version, the focus mechanism is much simpler and may have the ability to be modified as you suggest. Much depends on the nature of the close focus stop and how much travel is available on the focus helicoid. On many lenses, the infinity stop is adjustable and the close focus is not.

If you are just wanting to use your J-9 for occasional close-focus work, I would suggest a short extension tube as your easiest option.


Steve
09-15-2012, 08:28 AM   #4
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QuoteOriginally posted by stevebrot Quote
If you are just wanting to use your J-9 for occasional close-focus work, I would suggest a short extension tube as your easiest option.
+1 to this. Getting the MFD from 80cm to 50cm isn't worth mucking about with the internals (and probably screwing up infinity focus)... heck even a "flanged" M42 adapter will lower your MFD to some degree!

09-15-2012, 02:37 PM   #5
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Yes my version is M42.

I did figure that the link may have been the M39.

I do have extension tubes. 10mm being the shortest. From what I remember the post had mentioned that MFD was altered unaffecting
infinity focus.

I sort of hate switching tubes and lenses. My sensor is dirty enough as it is.

I'll check out the Russian lens forum.
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