Carl Zeiss Jena Sonnar 50mm f2 vs Jupiter 8

memetph · Joined: 01 Dec 2013 Posts: 942 Location: Poland

After reading the « facts » or so called , I come back to my experience with those lenses.
The performance of my Helios 104 samples is not more consistant than the one of my J8s M.
Quality control was not better.
I would say the same about my KMZ lenses. You have to sort out good samples what ever the date of production.

fiftyonepointsix · Joined: 30 Apr 2017 Posts: 292

https://www.youtube.com/watch?v=oNm3WqveUYc

The J8M went through several revisions, similar to the J-3. The first version of the J8M has a separate fixture for the rear doublet, as seen in the above video of a CLA for a 1959 J8M. Several websites state that production of that type ended ~1967.

This is one site that shows the evolution of the external appearance of the J8M.

http://www.sovietcams.com/index.php?1831276576

I also picked up a PT3565 Arsenal made J-8, was converted to LTM using a Tabbed I26 focus mount. (Edit- took the rear doublet out, it is the same as the KMZ J8. I'm not taking the whole lens apart, but the Arsenal J8 appears to be the same as the KMZ J8 of the period)

The J8M's that I have taken apart were made after 1967, and had a one piece barrel, with the rear group held into the main barrel with a retaining ring. It did not have the separate fixture as shown in the youtube video.

The optical design was obviously changed during the production run. The two 1960s J8M's that I shot with on the Kiev's were awful, used them once and replaced with Helios-103 and a Menopta 53/1.8- which is a 1990s rebadged Helios-103. I've shot with another J8M that was converted to LTM sent to me for repair, I had to swap out the optics on it. (Side-note, I bought 12 Menopta 53/1.8's, shimmed them for Nikon S-Mount, and sold them on RFF)

Shot with four of these before buying another in LTM-

I bought a 1972 J8M that had been converted to LTM using a Canon 50/1.8 focus mount.

https://cameraderie.org/threads/jupiter-8m-50-2-adapted-to-leica-mount-using-canon-50-1-8-mount.39496/

It is very good. After taking apart the 1973 J8M, I suspect it uses the newer optical formula.

SO- this is a complicated story, and the answer of what to look for in a J8M is not easy. At some point the lens was completely reformulated, using a classic Triplet for the middle group. Around 1967 the J8M was simplified, the one-piece barrel is the external difference. You are also dealing with sample-to-sample variation in quality. If you get a good J8M, keep it. I have had two good ones out of a total of 5 tried, includes the one sent back out after swapping the optics. My good one is in LTM, got it for $50- could not buy the parts for so little money. I am not going to take it apart. But I am going to look for an early J8M to satisfy curiousity. I will take pictures, I do for most of the lenses I take apart.

fiftyonepointsix · Joined: 30 Apr 2017 Posts: 292

Looking around the Internet- I found discussions from 15 years ago of the J8M having two elements collapsed into one.

I took apart the 1969 J8M that I use more as a body cap, as the performance of the lens was terrible. The middle group matches the one I took apart in 2013.
Put it and the rear group into an acetone bath for two days- got rid of the paint, made it easy to find the seam on the rear doublet. I still could not see or feel anything on the middle group. Usually you can see some spill-over of the cement used on the elements, or feel a seam with your fingernail- nothing.

> (I'm not even sure how one can prove there's only two elements without cutting the whole damn thing in half lengthwise)

Heat the group to several hundred degrees. Usually Canada Balsam will melt, or at least bubble. Makes finding the elements in the groups easy. Does not always get them apart, sometimes it does. But- easy to find the elements in groups. This did NOT work for this group. No bubbling, no discoloration.

50+ years ago, we used to bake clear marbles in the oven and then pour cold water on them. Do it just right, get pretty cracks in the middle of the marble.

Don't repeat this experiment without eye protection- which I have.

It's a triplet. It is simplified as it has two flat surfaces internal to the group, and that the reduced diameter of the rear element uses less glass than the traditional triplet of a J8.

SO Why did Arsenal completely redesign this group?

I am speculating that this triplet is difficult to manufacture, that centering the 2nd and 3rd element (different diameters and flat surface to flat surface) in the group is a problem. All of the late 1960s J8M's that I've shot with were poor performers.

The newer triplet has the same diameter for all three elements. We do not have a diagram for the new triplet- and I am not destroying the one I took apart or the one in my really nice/good performing J8M in LTM to find if the inner surfaces are curved or flat. The 1970s J8M I have that was converted to LTM is a great performer. SO- whatever drove Arsenal to change the formula in the early 1970s was well worth it. There must be a reason behind it, but we'll probably never know.

visualopsins · Expire: 2025-04-11

Two flats for moire?

fiftyonepointsix · Joined: 30 Apr 2017 Posts: 292

iangreenhalgh1 · Expire: 2014-01-07

The reason for the fall off of quality control in the mid 60s is the centrally planned economy of the USSR - there was a diktat issued from on high to greatly increase production, which was done, but corners had to be cut in areas such as QC.

This was a very common thing in the USSR, it is why so many of the apartment blocks were shoddily built - throw them up as quickly as possible to fulfil Moscow's imposed quotas. Boris Yeltsin was (in)famous for this, his career pre-politics was in managing the building of apartment blocks and he was very successful as he got a lot of them built, but in order to do so he cut a lot of corners and the blocks were of terrible quality.

fiftyonepointsix · Joined: 30 Apr 2017 Posts: 292

gi0rgi0ba · Joined: 16 Nov 2017 Posts: 38

Hi, please could someone tell me the diameter of the Jupiter-8 and 8M internal thread seen in this image?

Thanks in Advance
BR
Giorgio

D1N0 · Joined: 07 Aug 2012 Posts: 2491

One of these will tell you

gi0rgi0ba · Joined: 16 Nov 2017 Posts: 38

yes I know the instrument to use to take the measurements, my question was related to the jupiters thread diameters in the picture (LTM left and KIEV on the right), which I do not have. Please is there someone who could take these measurements?