Jupiter-3 Close Focus Mod

If you do not file down the mount, different cameras lose coupling at different distances. The Canon P will follow my modified J-8 all the way to 0.7m AFTER filing the mount. Without filing, most lose coupling at between 0.8m and 0.85m. The Zorki 3M can follow the cam farther in, as the "finger follower" is used. Cam following Wheels lose coupling more quickly than the FSU cameras. Best to file down the mount by about 1 thread.
 
Thanks Brian

Thanks Brian

I asked because my J8 at min focus, the inner ring of the lens was already inside the lens body, and followed coupling down to .6m on the m8 (with shims).

I did take the lens apart today using your pdf instructions (took me a while to figure out that to unscrew it, it's not unscrewing the focus barrel from the mount, but the front aperture area thing from the mount/focus barrel.

Anways, took that little black screw out, twisted it a bit, and put it all back together, and while focus was ~.8m to full infinity with no shims, the aperture was stuck closed at like f16 or so.

So I took it apart again and after a bunch of twisting and turning stuff, I just couldn't get the aperture to open up until I inserted that black little screw.

So with the screw in I opened it up all I could twist, which I don't think is wide open, but maybe like f2 or 2.8 and put it back together. My goal was to try to get it all the way to 1.5 or more open, then close it all together, but it appears that where it is rotated when you lock the screw down will affect how much you can open the aperture.

I might have a different variant than the ones you have, because I can't see any way in which the outer focus barrel has any impact on distance other than moving the inner focusing thing. The inner element simply screws into the mount/focus barrel until it is tight with the aluminum shim in there.

I can see how you can cosmetically remove the 3 screws to align up the distance scale independently of actually getting it to focus closer, but that is trivial for me, I'm looking for functionality here, and don't have a screwdriver that tiny anyways.

I wonder if someone put some rare expensive element inside the cheap chrome '70s aluminum assembly and that's why it's not quite the same as what's in your pdf pictures and ones here?

There's also some cryptic hierglypics scribbled on various parts of the internals. Perhaps it's a pre-war prototype designed for the KGB or something (collectors - make offers!) 😉

Brian Sweeney said:
If you do not file down the mount, different cameras lose coupling at different distances. The Canon P will follow my modified J-8 all the way to 0.7m AFTER filing the mount. Without filing, most lose coupling at between 0.8m and 0.85m. The Zorki 3M can follow the cam farther in, as the "finger follower" is used. Cam following Wheels lose coupling more quickly than the FSU cameras. Best to file down the mount by about 1 thread.
Click to expand...
 
Last edited:
I'm going to post a thread on the modified J-8 soon. Rememer that when you use the shim under the lens, the threads unscrew as much as the cam. So it is the equivalent of filing the mount down for a lens that has been modified to focus closer using the helical.

The Black J-8 is the easiest-yet lens to modify for close focus. Remove the close-stop screw, move the fixed stop screw out ~0.1mm so that the far-stop screw acts for both directions. Thread probably this weekend, a few more pictures needed.
 
Thanks Brian

Thanks Brian

Would it help if I took some snaps of my silver J3 to see if it's even serviceable? Much of it looks like the one(s) in your great J3 PDF, but some things are just different, like the silver 1mm retaining ring, I don't think I have that part, but I do see some silver on the edge of the black threads going into the lens body.

I don't have a mini screwdriver small enough to get the mount barrel parts diassembled, but might be able to find at a store in day or two, it looks like about 1 or 2 sizes smaller than what I have, which are eyeglass type screwdrivers. I also think I need some kind of thin spanner wrench to move what seems like may be a movable part between the front black lens hood ring, and lens body, seems like about 5mm wide that I can't quite grasp.


Brian Sweeney said:
I'm going to post a thread on the modified J-8 soon. Rememer that when you use the shim under the lens, the threads unscrew as much as the cam. So it is the equivalent of filing the mount down for a lens that has been modified to focus closer using the helical.

The Black J-8 is the easiest-yet lens to modify for close focus. Remove the close-stop screw, move the fixed stop screw out ~0.1mm so that the far-stop screw acts for both directions. Thread probably this weekend, a few more pictures needed.
Click to expand...
 
Last edited:
Okay, I have read the close-focus mod guide. Many thanks Brian. I will see if I can get time to do this over the weekend. I am more than a little nervous about this. It's already a really fantastic lens - so I have a lot to loose if I screw this up....

[nervously wiggles his sweaty, jittery fingers]
 
So I did the close focus mod. Works just fine. Lens still focusses great. Optics still sharp. NO problems at all - it was just a question of holding my nerve!
 
Congratulations! The worst of it is filing the mount down.

The first two J-3's that i worked on were misassembled messes. Nothing to lose by taking them apart. bought 4 of them just to learn how to do it.
 
Just took a handful of photos with both cats. Haven't put the card on the PC yet, but on the M8 LCD, .7m looks perfectly sharp! Tonight the cats, tomorrow infinity!!
 
Ted- "To Infinity and beyond!"

The lens will now go past infinity. You will find the spot that allows focus wide-open and at infinity with this modified lens. Most J-3's that are shimmed for close-up and wide-open need to be stopped down for use at infinity. This lens corrects that.
 
awesome!!

awesome!!

I once sold a lens to a collector type guy. He thought the lens didn't focus to infinity.

I had to explain that the collapsible lens, needed to be uncollapsed.

Oh, and then that it had to be rotated to the infinity mark!! 😛

Already dark, but maybe I can shoot the moon if it's out! Will also be great for use with a NEX if the adapter isn't just the right length!

Brian Sweeney said:
Ted- "To Infinity and beyond!"

The lens will now go past infinity. You will find the spot that allows focus wide-open and at infinity with this modified lens. Most J-3's that are shimmed for close-up and wide-open need to be stopped down for use at infinity. This lens corrects that.
Click to expand...
 
OK, here are some snaps with my Sweeny modified later silver J3 at .7m wide open! Incredible! If b/w, then I was in b/w mode. M8 ISO 2500 is great with this lens! more here

1049514927_XvR6R-L.jpg


1049513723_jbZwP-L.jpg
 
Last edited:
Well since .7m is coupled and spot on, it's now time to shim and see if I how close I can get before I lose coupling, perhaps my M8 will give me a few more inches.

It's great that it is setup for beyond infinity, so if the shim works for a few more inches close focus, I can just leave it there, and still get perfectly sharp infinity!
 
well, adding a shim to the Sweeny modded .7 to just beyond infinity J3 is getting me about 4 more inches, but without coupling, so I'm going to take it off. Even with digital and chimping, it takes 2-3 shots when not coupled to nail the focus.

I think the .7 or .65 where it's at is at about without shim, is at the the limits of close focus coupling. A piece of foil would be interesting, but it's not sturdy enough for my liking.

When I get a micrometer, I will see how thick my thinnest plastic shim is, and see if there is anything thinner that could be durable too.
 
Hi Brian

Hi Brian

Yes, can't wait until I have a NEX to use this on.

Have you tried a shimmed LTM 28 on your u4/3 or NEX? Amazing, you can get down to ~10" with a standard credit card shim with the M8 (lose RF coupling around .6m) though.

Brian Sweeney said:
Liveview cameras are the best bet for under 0.7m. The modified J-8 has no problem at 0.5m.
Click to expand...
 
Look at Post #4 in this thread:

https://www.rangefinderforum.com/forums/showthread.php?t=173038

Picture #1: shows the guide screws that hold the main portions of the helical together. The screw at the bottom: this controls the focus throw. The head of the screw turns in the cut-out, sets min and max focus. You can remove the screw completely, the guide screws will allow closer focus and focus past infinity. For the Jupiter set to focus on the Leica: this helps achieve infinity focus after shimming the lens for close focus. You can either remove that screw, or file down the slot that it travels in.

After modding the lens for closer focus, you must file down the threads of the focus mount to allow the RF Cam follower of the camera to travel deeper into the lens mount. See reply #7 of the thread- best to file down the focus mount when it has been disassembled. Screw it onto the camera to mark the section that needs to be filed down, the part of the mount that the RF cam follower needs to line up with.
 
close_focus_mod.jpg

I just put this together from some pictures of a CLA. I will look for the original images- I used a Nikon E3 DSLR circa 1997 for them.
Until then- there are two steps to this- the trick is to increase the focus throw, easy way: remove the stop screw. The Guide pins will stop the lens at close distance. You can also increase the ridge.
 
You must log in or register to reply here.
Back
Top Bottom