Jupiter 12 35 mm f/ 2.8 Lens Manual
Collimating a Jupiter 9
Over the past few years, I have been asked not only to service Jupiter9’s but also to collimate them
so that they work well with Leica and other Leica standard cameras. Recently I was asked to do
another so I thought I would record it so that others can try if they so wish.
There are all sorts of arguments about the Leica standard v FSU standard and also about quality
control. Personally, I think it is a mix of the 2. Certainly every one of the 20 or so lenses I have
done has been a little different. However, the main problem is that if the lens is set to focus
correctly at infinity, then at close distances the lens actually focuses slightly (or sometimes quite
far) behind where the RF says it should.
First a little theory. Any RF albeit Leica, Voightlander or FSU is set to focus a “standard” 50mm
lens. Most 50 mm lens have an extension from the front (moving) barrel to act against the cam. To
use any other lens, the RF tab must be “geared” so that it tab moves as for a 50mm lens despite the
amount of movement actually required by the lens group. Hence the double helix in the J9. If this
ratio is not correct, then the lens will not focus correctly throughout the range. To correct the
problem, you would ether have to alter the gearing or change the focal length. In the case of a J9,
altering the gearing would mean making a complete new back unit which for me is impossible.
It is however possible to alter the focal length slightly by altering the distance between the front and
rear lens groups. As this is “set” using shims, it does become solvable problem. If the RF is set
correctly and the lens actually focuses on a point further back, the focal length needs to be reduced
slightly and vice versa.
To do this, you need a method of checking both the infinity focus and the close focus with regards
to the RF. At times I think a digital RF would make life much easier but at the same time there are
times when using my method works better.
I used to use a modified Fed 2 body. On this the rear of the body casing has been cut away, the
shutter curtains have been removed and an old SLR focus screen has been glued to the film rails.
When the camera is mounted on a tripod, I use an 8x lupe to check the focus on the film plane.
so that they work well with Leica and other Leica standard cameras. Recently I was asked to do
another so I thought I would record it so that others can try if they so wish.
There are all sorts of arguments about the Leica standard v FSU standard and also about quality
control. Personally, I think it is a mix of the 2. Certainly every one of the 20 or so lenses I have
done has been a little different. However, the main problem is that if the lens is set to focus
correctly at infinity, then at close distances the lens actually focuses slightly (or sometimes quite
far) behind where the RF says it should.
First a little theory. Any RF albeit Leica, Voightlander or FSU is set to focus a “standard” 50mm
lens. Most 50 mm lens have an extension from the front (moving) barrel to act against the cam. To
use any other lens, the RF tab must be “geared” so that it tab moves as for a 50mm lens despite the
amount of movement actually required by the lens group. Hence the double helix in the J9. If this
ratio is not correct, then the lens will not focus correctly throughout the range. To correct the
problem, you would ether have to alter the gearing or change the focal length. In the case of a J9,
altering the gearing would mean making a complete new back unit which for me is impossible.
It is however possible to alter the focal length slightly by altering the distance between the front and
rear lens groups. As this is “set” using shims, it does become solvable problem. If the RF is set
correctly and the lens actually focuses on a point further back, the focal length needs to be reduced
slightly and vice versa.
To do this, you need a method of checking both the infinity focus and the close focus with regards
to the RF. At times I think a digital RF would make life much easier but at the same time there are
times when using my method works better.
I used to use a modified Fed 2 body. On this the rear of the body casing has been cut away, the
shutter curtains have been removed and an old SLR focus screen has been glued to the film rails.
When the camera is mounted on a tripod, I use an 8x lupe to check the focus on the film plane.