J12 focusing

[Tun]

bought a J12 from a russian junk store. Found a mint J12 and decided to buy it for my Fed 2. However, after mounting the lens onto the body, i think the focusing is very off. Even when the object is 1m away, i set my focus to 1m but it still doesnt work. The focusing is only near after 3m.

Are all J12 like this?

Thanks
Tun

 

[Sonnar Brian]

No, they are not all like that. The one I had required setting the optics module, using ground glass and a loupe at the film plane with the camera set to "T". After that, the focus was fine.

 

[Tun]

hey, Brian

I have no idea on how to fix it? do u have any pics or better explanation to guide me?

 

[VinceC]

These lenses in Kiev/Contax mount also have a weird idosyncracy/design flaw that allows you to screw the rear element too far forward, shifting the whole focus too close. It's easier than it sounds, because you can end up knocking focus off simply when removing filters to being too heavy-handed when adjusting f/stops. All the optics can screw forward or backward in the mount. In most cases, the whole optical assembly ought to be screwed all the way back.

 

[Kim Coxon]

Hi Tun,
I can't help with diagrams at the moment but I will be giving a J12 a full service in about 10 days and I will put a sheet with photos on how to do it on my website with the others at http://pentax-manuals.com/repairs.htm

Kim

 

[Sonnar Brian]

I traded off the J-12, but did an entire roll with it. Results were quite good after adjusting it.

I did not document the work.

I'll be waiting for Kim's repair instructions as well.

 

[nomade]

I've a jupiter 12, and it's the most reliable lens i have, well it's not like i've many lenses anyway

 

[Tun]

Thanks Kim and everybody else. However i feel like trading off my J12. Using 50mm lens on fed 2 is still better than other lens which is my own opinion. I shall see how it goes. Bought things too impulsively.

 

[dll927]

Brian Sweeney - your list of cameras has a Minolta 16. By any chance, is that the little sub-miniature one? I bought one of those eons ago, but it was so hard to find film for it, and the couple of times I had prints made, they weren't anything to write home about. I may still have it, but I'll have to do some looking.