Originally posted by Ben_Edict Have you made some photos of the adjustment. I don't quite understand, which ring you refer to, so a photograph would be helpful. We had a lot of in-depth discussions about this lens in the manualfocus forum and some guys posted a lot of phtographs about their complete disassembly/re-assembly of that lens, but nobody mentioned this easy way to adjust focus - and I myself did not find it, too. Maybe the tinkerers amongst us always think too complicated!
Ben
Ben,
Flipped through my photos and realized I got so concentrated on figuring out the setup that I quit taking photos before I got to the solution. Took the lens back apart this morning to capture some images quickly. I'll give a quick description of the steps to get there first:
1. Remove the lens mount and ribbed retaining at the ring closest to the focussing group. (third ribbed ring from the camera mount)
2. Remove the scale ring (unsure of proper term) as shown in the first photo.
3. Looking from the camera mount end, look between the focussing ring and focussing assembly. There are three screws there as shown in photo 2. Remove these.
4. Now you will see the focus stop ring. photo 3. Most of it is parallel to the lens assembly, but has three tabs that are held in place by clamping force/friction when the lens is together. Someone etched the correct placement of those tabs on my lens. I'm guessing this was done by the original assembler. If yours has the same, it would likely confirm that idea.
To get proper infinity focus: I had to ignore the etch marks.
5. By grasping the ridge of the focus assembly the focus ring was screwed to, one can adjust the focus assembly. I turned it in completely so the helicoids were bottomed out (focus assembly is collapsed)
6. Then I extended it approximately 1/16th of a turn and placed the stop ring at this location and reassembled.
Note: to make sure your focus scales end up at the top of the lens again, have the lens set against the infinity stop during reassembly. The distance scale may not read correctly, but can be turned match again.
This adjustment gave me infinity and I don't think I lost much, if anything at the minimum focus distance. I didn't purchase this lens for photos of close stuff, so I wasn't overly concerned about that anyways.
I am assuming you've had the lens apart for taking care of the wobble, or at least have heard of taking out those little L-brackets and unscrewing the helicoid. I counted 6 or so thread leads, so I suspect that if someone took that helicoid apart and back together enough, they would be able to get it matched up the same way the assembler did during manufacturing. Adjusting this ring appears to simply compensate for catching a different helicoid than the assembler did.