Jupiter lens to LTM Leica shim always needed?
Old 09-01-2011   #1
summar
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Jupiter lens to LTM Leica shim always needed?

The title says it all. I have a Leica IIIa and am thinking of getting Jupiter-8 (early '60s) and Jupiter-12 (early '70s) lenses. I've read about shims being needed for accurate focus.
I've searched the RF forums thoroughly but can't find any specific info.
My questions: Is shimming always needed or does it depend on the individual lens? If shimming is needed for both would a shim for the J-8 and J-12 be identical in thickness?
Last question: Is making a shim a job for someone experienced in fine metalwork or might a novice be able to do it aided by clear instructions?
Any advice would be much appreciated.
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Old 09-01-2011   #2
je2a3
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Try the lenses first with a test roll. I never had issues with my J-8 and J-12 on Leica or Canon LTM bodies, even the J-3 wide open and they were not shimmed.
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Old 09-01-2011   #3
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There is a way to check I think.

Was it Brian Sweeney who does the conversions for people here?
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Old 09-01-2011   #4
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You will find lots of information and instructions in Brian's sub-forum. And as he's said, probably more than once, "if a software engineer can do this, so can you" (or words to that effect, sorry if I'm misquoting you, Brian).

Note that the shims are internal, and individual to each lens, even from one J-8 to another (for example). You're trying to optimize a lens that was not made to the exact Leica standard to begin with, had considerable variation even when new, and is now decades old.
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Old 09-01-2011   #5
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I have a Jupiter 8 and a 12 and both focus perfectly on my IIIf (and M9 with an adapter). I don't know the proportions of those that need adjusting to those that don't. But if you consider that nobody posts about their perfect lenses, and everybody posts about problems, then going on internet traffic the chances are that you will get a good one.

Steve
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Old 09-02-2011   #6
john neal
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Having done a few conversions, I would doubt that any J8 would be "perfect" on a Leica body - it might be very close if stopped down to f4 or smaller, or if the subject is 5m+ from the camera, but is that how you always take your pictures?

Every J8 I have looked at needed different shims to achieve critically acceptable focus at 3 - 5m or less when used at f2 or f2.8. Having done that, you then need to stop down to f2.8 or smaller for infinity to focus correctly. I'm sure brian will explain, but there is a focus shift for the Sonnar formulation (i.e. J8) between near & far focus. Confused me for a good while, but I now have a method for settin them up that works.

Unashamed plug - I will shortly be selling 3x J8 lenses (2x 1950s + 1x 1970s) and, probably, an uncoated f2 Zeiss Sonnar in a J8 mount. All have been set up for Leica bodies - I'm just processing the test shots now.

I have not worked on any J12 lenses, so can't comment on those directly - given the shorter focal length, I would expect there to be less of an issue - I have used a couple on Barnack bodies with good results, but generally not for close-up work.
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Old 09-02-2011   #7
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Quote:
Originally Posted by john neal View Post
Having done a few conversions, I would doubt that any J8 would be "perfect" on a Leica body - it might be very close if stopped down to f4 or smaller, or if the subject is 5m+ from the camera, but is that how you always take your pictures?
.
So there you go summar, its all crap, don't bother.

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Old 09-03-2011   #8
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Quote:
Originally Posted by 250swb View Post
So there you go summar, its all crap, don't bother.

Steve
I disagree - it's just diferent. If you like the creamy look and the superb bokeh, it is worth the effort.
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Old 09-04-2011   #9
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Missed this first time around!

The laws of Physics are at work here. Russian lenses are made to the Contax 52.4mm standard, Leica RF's expect a 51.6mm lens. The Russian lens requires 0.1mm more in translation when changing focus from 1m to infinity than a Leica lens. So- if you want close-up, wide-open performance you usually need to increase the shim by 0.1mm. Infinity- Sonnar focus shift works in your favor, stop down to F4 and the rear-ward focus shift gets infinity.

There is deviation in focal length in J-3's and J-8's, even Zeiss Sonnars. Sometimes you get lucky, and the focal length is closer to the Leica standard. This 1961 J-3 is closer to the Leica standard than most.

Close-up at F1.5:






And at distance at F1.5:



100% crop:


The shim of this lens needed to be thickened by 0.1mm, as do 80% of the lenses that I've seen.

Last edited by Brian Sweeney : 09-04-2011 at 06:15.
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