Minolta MC Rokkor 58mm f/1.2 mount conversion, part 5/5
Adjusting focus to infinity on the new lens mount
Here the black ring (with the focusing mark) has also been removed. The bright ring around the edge of the remaining lens can now be rotated. Its height changes as it rotates, i.e. it screws in and out. This adjusts the infinity focus position. It can be rotated in half-turn increments, as the black ring can only be reassembled when the gaps on are aligned with the focusing part underneath.
When rotating the ring, make a note of how much you've turned it, so you can return to the original position if necessary. Note that the entire front of the lens can now also be rotated freely (it is coupled to the focusing system by the black ring, which is now removed). It will also unscrew from the rest of the lens if you rotate it far enough. It is a real pain to get back on in the same place, so try not to rotate it.
The process of adjusting infinity focus is a process of trial and error. You need to reassemble the lens (with the new Minolta AF mount in place) and test it on a camera. If you can only focus at close distances, but not at infinity, then you need to rotate the ring so that it goes IN, i.e. down as we are looking at it in this picture. If you can focus past infinity (to an amount that you find distracting), you need to rotate the ring OUT, so that it becomes taller.
You may not be able to get the focus spot-on with just this. If you can get it to focus past infinity, however, then it's easiest to just live with it. At that point it is also possible to take away the excess range by inserting slices of aluminium foil (or just paper) between the M42 adapter and the mount spacer, though you'll need to be careful to get it flat if you opt to do that. Personally I chose to cut a stack of shims from aluminium foil, inserted the entire stack so I could no longer focus on infinity, then removed shims one by one until the infinity focus was perfect (see comment below for details if you opt to do this).
Sometimes, to get enough adjustment range, you may need to unscrew the entire focusing helicoid from the front, and reattach it at a different orientation. This is, as I said before, a real pain, but it affects the height of the entire system and gives you more range on the other ring. Personally I ended up doing this, but mostly because I accidentally unscrewed it at one point while I was figuring out the system (I didn't have this guide when I started =).
Anyhow, at the end of each step you need to reassemble the lens by following these instructions in reverse, mount it on the camera and check the infinity focus. The black ring (focusing mark) is reassembled by aligning the focusing mark with the infinity mark on the distance scale, and rotating the focusing system so that the hole matches the lever on the black ring, and then rotating the bright ring so that either gap aligns with the hole, and the screw holes align with those on the black ring when the lever goes in the hole. Best way to do this is to never rotate anything other than the bright ring, if you can manage it.
While checking, you can speed up reassembly by only using two screws from each pair of four, and you can also just omit the aperture ring for testing, as it doesn't affect the result (leave it wide open).
Best of luck, and a bit of patience!
Minolta MC Rokkor 58mm f/1.2 mount conversion, part 5/5
Adjusting focus to infinity on the new lens mount
Here the black ring (with the focusing mark) has also been removed. The bright ring around the edge of the remaining lens can now be rotated. Its height changes as it rotates, i.e. it screws in and out. This adjusts the infinity focus position. It can be rotated in half-turn increments, as the black ring can only be reassembled when the gaps on are aligned with the focusing part underneath.
When rotating the ring, make a note of how much you've turned it, so you can return to the original position if necessary. Note that the entire front of the lens can now also be rotated freely (it is coupled to the focusing system by the black ring, which is now removed). It will also unscrew from the rest of the lens if you rotate it far enough. It is a real pain to get back on in the same place, so try not to rotate it.
The process of adjusting infinity focus is a process of trial and error. You need to reassemble the lens (with the new Minolta AF mount in place) and test it on a camera. If you can only focus at close distances, but not at infinity, then you need to rotate the ring so that it goes IN, i.e. down as we are looking at it in this picture. If you can focus past infinity (to an amount that you find distracting), you need to rotate the ring OUT, so that it becomes taller.
You may not be able to get the focus spot-on with just this. If you can get it to focus past infinity, however, then it's easiest to just live with it. At that point it is also possible to take away the excess range by inserting slices of aluminium foil (or just paper) between the M42 adapter and the mount spacer, though you'll need to be careful to get it flat if you opt to do that. Personally I chose to cut a stack of shims from aluminium foil, inserted the entire stack so I could no longer focus on infinity, then removed shims one by one until the infinity focus was perfect (see comment below for details if you opt to do this).
Sometimes, to get enough adjustment range, you may need to unscrew the entire focusing helicoid from the front, and reattach it at a different orientation. This is, as I said before, a real pain, but it affects the height of the entire system and gives you more range on the other ring. Personally I ended up doing this, but mostly because I accidentally unscrewed it at one point while I was figuring out the system (I didn't have this guide when I started =).
Anyhow, at the end of each step you need to reassemble the lens by following these instructions in reverse, mount it on the camera and check the infinity focus. The black ring (focusing mark) is reassembled by aligning the focusing mark with the infinity mark on the distance scale, and rotating the focusing system so that the hole matches the lever on the black ring, and then rotating the bright ring so that either gap aligns with the hole, and the screw holes align with those on the black ring when the lever goes in the hole. Best way to do this is to never rotate anything other than the bright ring, if you can manage it.
While checking, you can speed up reassembly by only using two screws from each pair of four, and you can also just omit the aperture ring for testing, as it doesn't affect the result (leave it wide open).
Best of luck, and a bit of patience!