Close focus mod for 1964 Jupiter 8

[MarkWalberg]

I bought a 1964 Jupiter 8 from Ukraine on eBay that had a bit of fungus and that dirty look that the aluminum gets. Focus was very stiff. So, I used Kim Coxon's directions to clean it. This is his type 3. Except for a couple little fungus spots, it has pristine glass. It had a light yellow filter that has clearly been on its whole life.

When I saw how the close focus stop worked, it was clear that it would be easy to modify. The stop just jams into the back of the focus ring. So, I filed a section of that ring down. I flattened the head of the stop screw a bit, but that is not really needed. Now, it focuses to 28 inches, which is 0.7 meters. I might file a bit more to get even closer. This was really easy. It is easy to get the pitch correct - just follow the focusing threads.

Fungus cleaned out easily. Focus is smooth with just a bit of vacuum grease from my old ultracentrifuge days.
To clean up the grey aluminum, my 50+ year old tube of Simichrome worked best.
I'm using this on the Z6. So, I won't bother with the shims.
A very nice lens for $16 !

 

[MarkWalberg]

I filed further. It focuses to 24 inches now. The picture of the Sonnar is just to show the field at closest focus wide open.

There is a problem that arose though. There is a slot that the infinity stop screw slides in. At my closest focus now, it is just far enough down the slot to sometimes come out of the slot. Focus gets stuck then. However, wiggling the lens a bit gets it back in the slot. I haven't taken it apart again to see if there is an easy fix for this. In the meantime, if you do this to your lens, I would not file quite as far around as I did. I filed down the ridge about 120 degrees or so from where it stopped originally at 1 meter. A little less than that should be fine.

 

[justins7]

Can you share photos taken with the lens?

 

[MarkWalberg]

Well, I just finished this mod. I assume that you want to see how it does close up. Of course, the pics of the ruler and the Sonnar are taken with this jupiter. I haven't taken any more yet.
I'm betting that it will not give the detail close up that the Nikkor 55 that I used to make the close ups of the filing work on the Jupiter.
Nevertheless, there are times when closer focus with the Jupiter wouud be handy. If I can get some useful pics later, I'll post them.

 

[Sonnar Brian]

The single-helical Jupiter-8 is easier to modify for close focus. Basically invert the near/far stops, then re-index the scales. I did one like that. The mount threads must be filed for the RF wheel to follow the cam into the lens past 0.9m.

 

[MarkWalberg]

Can you share photos taken with the lens?

Here is one taken at closest focus of 24 inches. Highly compressed jpg.

 

[MarkWalberg]

Here is one taken at closest focus of 24 inches. Highly compressed jpg.

View attachment 4831783

Can you share photos taken with the lens?

Here is another, again at 24 inches.
It was cold today here in Dallas, 21 this morning. I found that I have to get that Beckman vacuum grease out. In the cold, it I had to really work at turning the focusing helical. Will replace soon with lithium grease.

 

[MarkWalberg]

I did another one today. Focuses to 25 inches. Easy to do. I advise filing to less than 120 degrees by a few millimeters, say 115 degrees from where the guide screw first hits the focus ring. At about 120 degrees, the guide pin comes out of the slot at the front of the lens mount ring at closest focus and the lens can get stuck at close focus. So, better to stay a bit less than 120 degrees. It would be possible to modify the guide screw so that it didn't do this, but I haven't tried. Also, there is no need at all to file the guide screw.