ludoo
Established
A couple of days ago I received the J-12 I bought from a russian ebay seller. It looks in very good condition, the only "problem" with it are a couple dust spots on the inside surface of the back lens.
I unscrewed the rear element, but have no idea how to open it to clean it inside. Any help appreciated. Oh, and should I have marked where the rear element separated from the lens for reassembly? I did but the pencil mark disappeared...
I unscrewed the rear element, but have no idea how to open it to clean it inside. Any help appreciated. Oh, and should I have marked where the rear element separated from the lens for reassembly? I did but the pencil mark disappeared...
blacknoise
Established
I'm not really an expert in this matter, but I think the lens element should screw all the way in, and their should be only one entry point for the thread, so the line was unnecessary. I might be wrong though. As far as cleaning goes, I would avoid touching it with anything, if it is just a bit of dust (which, IMHO would not affect image quality), I would just use a blower to blow the dust out.
Hope this helps.
Rob
Hope this helps.
Rob
wolves3012
Veteran
If you've removed the rear element, just clean it with a lens cloth or blow off any dust, You can't disassemble the element itself, it's cemented together. As blacknoise says, there should be only one entry point and it will go back on without any special positioning.
ludoo
Established
Uhm, the specks of dust are inside the rear element. And by cemented you mean the assembly, not the lenses I hope? Because on mine the lenses cannot be separated, but they can be twisted in place.
ath
Well-known
This is the cross section of the J12:
left - subject
right - film
The three elements on the right appear to form one block on my J12 which can be screwed off but not disassembled. There seems to be an air gap in the block.
left - subject
right - film
The three elements on the right appear to form one block on my J12 which can be screwed off but not disassembled. There seems to be an air gap in the block.
ludoo
Established
Thanks Andreas! I guess I'll have to live with the dust then, and hope the fact that the inner lens of the end block turns freely is not a problem. 
wintrmute
Newbie
Did anyone ever work out if the rear element-group could be separated to be cleaned?
I've just picked up a Jupiter-12 that's in good condition except for some dirt that seems to be trapped inside the rear mushroom-like group..
The rear part twists, and at first I thought it'd unscrew, but no such luck.
I've just picked up a Jupiter-12 that's in good condition except for some dirt that seems to be trapped inside the rear mushroom-like group..
The rear part twists, and at first I thought it'd unscrew, but no such luck.
santino
FSU gear head
I'd say live with the dust. It won't affect your pictures and the lens too.