k__43
Registered Film User
So here is the story ..
I was avoiding the J3 for years, knowing that problem with the non-standard focal length and often misaligned copies. Since I got my M9 I had a more immediate way of checking focus than doing that with matte screens, loupes and film. So I got one from a guy that said he adjusted close focus for his M8, well he was right, but it was pretty off in any other aspect.
I wanted to change close focus so I "went in"... the adjustment is fairly easy to be honest. The problematic part was that I marked the inner cam module with permanent marker but I cleaned everything with isopropanol so my marking was gone. With 2 or 3 tries I found the correct starting angle (I already thought I fu¢ked up).
I was lucky to get a copy where the whole focus module was done right, I haven't had to drill new holes like described in that manual by Brian Sweeney.
Important tip here is I guess, you do not have to unscrew the inner cam anyway. It's a three part assembly and after you remove the two guide screws and the stop screw, you can just get off the outer part and there is the bit that needs some filing. When putting it back together the thread (on my copy at least) catches approx. where the stop screw hole aligns with the 1m stop.
All I had to do now was to file down a good bit on the M39 mount thread at the RF roller position, so that the roller can actually follow that far.
Easy job actually all in all!!
Btw, if you want to figure out how much to file away on the close focus stop, there is an easy solution! I tried to calculate it and found out later that it's actually just that easy: Unscrew the stop screw but leave the assembly together, put it back in the mount, mount it on your camera, focus to the closest point you want to achieve, unscrew it from the mount part without changing the focus and then mark where the stop screw hole is, this is how much you need to remove.
So that other thing I'm struggling a bit with is the lens module. What I noticed was that the rear triplet was slightly unscrewed, the shim is pretty thick and the fine adjustment stand off was on its far out side. I though that can't be right! .. check:
http://ussrphoto.com/Wiki/Content/files/1570/Jupiter_focal_length_adjustment.pdf
I screwed the rear triplet all the way back in and the stand off ring as far in as I could. I still can't reach infinity at f/1.5 (I couldn't before either) and the lens has some front focus that starts showing at 1.5m already and is quite heavy at around 3m (20 cm maybe). Well the closest focus seems to be okish (see pic --> 70cm f/1.5, focused at the butterfly wing)
I'm not sure if I have to reduce the shim thickness or if the focal length is still so much too long. I have the feeling that I have front focus all the way thru the focus range, so I guess i will start with thinner shims.
Also the aperture ring is stuck .. like glued on the lens module so I can't align it with the little red dot mark 🙁
MOST IMPORTANT TIP .. DO NOT LOSE THE LITTLE SCREWS (yes I'm yelling) - a magnet and a clean place is your friend
I was avoiding the J3 for years, knowing that problem with the non-standard focal length and often misaligned copies. Since I got my M9 I had a more immediate way of checking focus than doing that with matte screens, loupes and film. So I got one from a guy that said he adjusted close focus for his M8, well he was right, but it was pretty off in any other aspect.
I wanted to change close focus so I "went in"... the adjustment is fairly easy to be honest. The problematic part was that I marked the inner cam module with permanent marker but I cleaned everything with isopropanol so my marking was gone. With 2 or 3 tries I found the correct starting angle (I already thought I fu¢ked up).
I was lucky to get a copy where the whole focus module was done right, I haven't had to drill new holes like described in that manual by Brian Sweeney.
Important tip here is I guess, you do not have to unscrew the inner cam anyway. It's a three part assembly and after you remove the two guide screws and the stop screw, you can just get off the outer part and there is the bit that needs some filing. When putting it back together the thread (on my copy at least) catches approx. where the stop screw hole aligns with the 1m stop.
All I had to do now was to file down a good bit on the M39 mount thread at the RF roller position, so that the roller can actually follow that far.
Easy job actually all in all!!
Btw, if you want to figure out how much to file away on the close focus stop, there is an easy solution! I tried to calculate it and found out later that it's actually just that easy: Unscrew the stop screw but leave the assembly together, put it back in the mount, mount it on your camera, focus to the closest point you want to achieve, unscrew it from the mount part without changing the focus and then mark where the stop screw hole is, this is how much you need to remove.
So that other thing I'm struggling a bit with is the lens module. What I noticed was that the rear triplet was slightly unscrewed, the shim is pretty thick and the fine adjustment stand off was on its far out side. I though that can't be right! .. check:
http://ussrphoto.com/Wiki/Content/files/1570/Jupiter_focal_length_adjustment.pdf
I screwed the rear triplet all the way back in and the stand off ring as far in as I could. I still can't reach infinity at f/1.5 (I couldn't before either) and the lens has some front focus that starts showing at 1.5m already and is quite heavy at around 3m (20 cm maybe). Well the closest focus seems to be okish (see pic --> 70cm f/1.5, focused at the butterfly wing)
I'm not sure if I have to reduce the shim thickness or if the focal length is still so much too long. I have the feeling that I have front focus all the way thru the focus range, so I guess i will start with thinner shims.
Also the aperture ring is stuck .. like glued on the lens module so I can't align it with the little red dot mark 🙁
MOST IMPORTANT TIP .. DO NOT LOSE THE LITTLE SCREWS (yes I'm yelling) - a magnet and a clean place is your friend


