Loving this J3 - with help from Mr. Sweeney

I see.

In a modified Nikon 55/1.2 for Leica M I have made in the past, that modification was needed. I have a device than check at the same time the focus of the lens and measure the relative position than should have the rangefinder cam by mean of a indicator.

In the case of this 55mm lens, the correction was of 0.5mm. The Contax helical used in the lens had a pitch of 4.5mm for a 50mm lens ( I guess than the Sonnar is exactly 50mm ) thus the 55mm lens is 10% more long than 50mm and the helical should have a pitch of 4.95 being the 0.5mm the correct correction with a error marging of 0.05mm.

I think than the cut of 0.1mm is logic for to reduce focusing problems, I would know the opinion of users of my adapters about this theme, may be I must make them already corrected.

Regards,
Amedeo.


Brian Sweeney said:
Roland put a cut into the RF cam of his adapter to translate the motion of the 52.4mm focal length of the Contax to the motion expected by the RF pickup of the Leica. Basically, it looks like the cut-cam on the M-Mount Summicrons to correct for slight deviations in the focal length. The motion of the Contax Helical "overdrives" the RF pickup without this cut.

I'll get some close-ups of the cut, again it is very shallow.
Took some, posted here:

http://ziforums.com/album.php?albumid=176
Click to expand...
 
A big thank you Brian....I am enjoying the lenses you have worked on more than I expected and will not part with any of them. This is with my Jena 1.5/J3 ltm conversion stopped down to f2.

3973908373_07c30468df_b.jpg
 
I bought last night a 1951 J-3 made by KMZ in Contax mount. Brian gave me the go ahead nod, and I clicked on BIN. The lens looks incredibly shiny and new, and it has the look of a German lens. Most likely, it will have some German parts in it. Some people told me that Contax mount J-3's were usually produced in Kiev and that KMZ made LTM J-3's. Must be incorrect information.
 
After exchanging e-mail with Brian a few months ago I got around to purchasing a J-3 last night. And am anxious try it out.

Mine is a 1956 produdtion in LTM.

Can't help but think that these will be very hard to find in a few years.
 
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I agree with you. That's why I am adding a couple of J-3's, but I am getting Contax mount lenses and use them with an adapter on LTM cameras. I am still trying to better understand how the J-3 in these two lens mounts differs with respect to optimal focusing wide open.
 
raid, Brian: are these Contax mount lenses optically similar to the LTM ones? What I mean to ask is, are they from the same production line? In terms of the elements used ?
 
I am told that the lenses are identical optically. Even though KMZ makes mostly LTM J-3 lenses [I am told], I bought a Contax mount J-3 made by KMZ.
 
I seem to remember reading (on this forum) that the Contax J3's were "better" optically than the LTM's but that's really not my thing.
 
Brian has written on RFF that the shimming for a Contax camera is better done than the shimming for a LTM camera. In that sense, the J-3 in Contax mount is "better optically". Else,it should be identical, except for production variations in the FSU. If a factory is known to produce lenses with higher precision than another FSU company,and if one company focuses on LTM mount lenses while the other focuses on Contax mount lenses, you would expect that differences in optical qualities.
 
Taken with a '57 J-3 on my Leica IIIc, before all the trouble with the stuck aperture ring.

Scana0050.jpg


Brian, I'd like to send my J-3 to you for a CLA one of these days. I simply haven't got the tools to unscrew the rear lens elements for cleaning. The rubber friction mat didn't cut it and I haven't got the spanners for it.
 
What year is the J-3? The ones after 1963 or so have a one-piece optics fixture, rear element held in with a retaining ring. The older ones are easier to remove. I have the spanner, an inexpensive $25 item similar to many on Ebay.
 
1957. Hmm, I'm not a hero when it comes to disassembling optics, But as you say the rear elements should come out as one piece if I can only get the thing unscrewed. The lens has some condensation drying marks I want to clean out.
Point me to the right tool and I'll see what I can do ;)
 
I had a J-3 a while ago, but sold it. Stupid action, since I missed it the day I sent it off.

I considered the Nikkor 50/1.4, the Sonnar 50/1.5 (1/3 click stops, which would seriously mess with my head) and the Canon 50/1.5.

Two days ago I bought a near mint 1952 J-3 (serial 52000XXX) and in the process decided to let go of my beloved M-Hex 50/1.2. It's in the Classifieds.

I honestly feel the Sonnar look is that good for my portrait work when shot wide open. It will team up with my M-Hex 50/2.0, a Canon 50/1.2 and a Topcon 50/3.5.

Think I got this focal length covered now :D
 
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