J-3 parts lens would not focus

dexdog

dexdog

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So, I have a 1957 Jupiter-3 that I bought as a parts lens. I was not expecting it work, and it did not! But not in quite the ways I expected. Original lens would not focus at any distance, figured the helical was put together wrong. Swapped in a different optical block with same result. Took the focusing mechanism apart, found a couple of sets of scratch marks on the internals, someone had been in the lens before. Soaked the helicals in alcohol overnight, still had to use an old toothbrush to get last of the sticky grease off. Assembled correctly, nIce and clean now with new grease, very smooth.
 
I test-drove a couple of shims, spun an optical block from a 1958 J-3 into place, close focus and infinity both work at f1.5, although a measured one meter mark shows up a bit over a meter on the focus scale. I put the original 1957 optical block in to the focus mount, and was surprised that it would not come into sharp focus at all. I could get an image of sorts to form, but it was a barely discernable mass of coma highlights, kinda surreal. Optical block on the left works, one on the right does not.
 
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I removed rear triplet and front element from the 1957 optical block, looked pretty normal. Middle triplet was screwed in tight. Removed middle triplet and replaced it, assembled lens, still will not produce an image. What is going on with this optical block? Just trying to understand why it does not work. I dont really need the 1957 optical block for anything, it is just around as a parts lens (especially those tiny grub screws).
 
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Do the three groups look correct?
I've seen lenses assembled with glass from the wrong type lens to make it look complete.
With the front elements out- see where the projected image is formed. Hold under a room light, eyeball how far the formd image is to the lens.
Then do the same with the Rear groups. Both should form an image.
 
Sonnar Brian said:
Do the three groups look correct?
I've seen lenses assembled with glass from the wrong type lens to make it look complete.
With the front elements out- see where the projected image is formed. Hold under a room light, eyeball how far the formd image is to the lens.
Then do the same with the Rear groups. Both should form an image.
Click to expand...
So, rear groups look normal on both lenses, form an image at same distance from the eye. The middle group on the 1957 lens will not form a normal image, while the one from the 1958 does OK. The middle group from the 1957 looks like a regular J-3. I guess this is just another case of not knowing what has happened to a lens in the last 68 years! Thanks, Brian!
 
Too much time has passed, one day I was brought a Biogon from 1938-1939, bought and brought from Germany.
It was sharp at a distance of 0.5-1.5 m. Upon careful examination it turned out that the rear lens block ("mushroom") and the front lens were not from Biogon.
I found a way out of the situation, but it required turning work.
In fact, about 30-50% of Biogon remained there.

Partial replacement of lenses for lenses of different years is usually not possible.

An interesting point - I just today, literally just now, adjusted my Jupiter 3 after a long break in use, now I’ll go check it.

😉
 
dexdog said:
So, rear groups look normal on both lenses, form an image at same distance from the eye. The middle group on the 1957 lens will not form a normal image, while the one from the 1958 does OK. The middle group from the 1957 looks like a regular J-3. I guess this is just another case of not knowing what has happened to a lens in the last 68 years! Thanks, Brian!
Click to expand...
The middle group should not be able to form an image, it has a negative focal length.
I have lots of spare middle triplets for ZOMZ.
 
Sonnar Brian said:
Do the three groups look correct?
I've seen lenses assembled with glass from the wrong type lens to make it look complete.
With the front elements out- see where the projected image is formed. Hold under a room light, eyeball how far the formd image is to the lens.
Then do the same with the Rear groups. Both should form an image.
Click to expand...
So, rear groups look normal on both lenses, form an imageat same distance from the eye. The middle group on the 1957 lens will not form a normal image, while the one from the 1958 does OK. The middle group from the 1957 looks like a regular J-3. I guess this is just another case of not knowing what has happened to a lens in the last 68 years! Thanks, Brian!
 
Sonnar Brian said:
The middle group should not be able to form an image, it has a negative focal length.
I have lots of spare middle triplets for ZOMZ.
Click to expand...
I dont know which is which now! Took both out. I have a 5 spare middle groups for ZOMZ, but thanks anyway. I bought the parts lens because I wanted the focusing bits, so it was worth it, I am pondering converting an old KMZ in Kiev mount.
 
Middle group will form an image, it is even right with the world. Rear group will form an image too, but upside-down. This is middle group
 
dexdog said:
Middle group will form an image, it is even right with the world. Rear group will form an image too, but upside-down. This is middle group
Click to expand...
I meant it does not project an image- put a piece of white paper on a surface, under a room light. Now try to use each group to project the image of the light to the paper.
 
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