One of these days I will find enough hours in the day to complete some of the projects I have promised. I keep intending to photograph each lens strip and re-lube I do and then combine it all in a PDF doc for inclusion here and the website. However, each time I come to do a lens, I am short of time and promise myself it will be the next one. :bang:
Anyway some thoughts on the J9. There are really 2 issues. The focus helix and the lens unit. As far as the focus helix is concerned, providing you put it back together in the right order and in stages, it is not that difficult to get back together correctly, even without marks. The reassembly of this is what will affect what the RF says in comparison to the focus scale on the lens and it is important to get this right first.
The second issue is setting the lens unit the correct distance so it is in focus when the RF and lens scale say the correct distance. So far I have been lucky and the only adjustment I have had to make is with the "main" lens unit. This is adjusted by the shims (coarse) and the threaded ring (fine) which sits behind the main unit. In theory if this is correct, it should focus throughout the range. The rig I use for this has been the Bessa R body and an SLR with a mgnified finder and known good lens. I am about to modify an old "parts" Fed as a dedicated body to do this. A piece of ground glass or flat clear plastic with a pattern drawn on it is fitted to the RF body. The back is left open with a bright white surface behind it. Set up the slr so you look through the SLR lens then through the RF lens. With both lens set and the same focus the pattern on the ground glass should be sharp and in focus. I start at infinity. I find this a lot easier than trying to use a loup and judgeing the distance from an object.
Now we come to the more difficult bit. There is also a shim for adjustment behind the rear group of the lens unit. I don't know whether Brian will agree but I believe that adjusting this will make a small adjustment to the effective focal length of the lens. and it is the relationship between this and the amount the cam moves that will ensure that the lens is in focus throughout the range. With a 50, there is not too much of a problem as the camera cam is usually set for this. The purpose of the double helix is to convert the movement of an 85 to the effective movement of a 50. If your length is not 85, the transposition will be wrong. So I would set the lens up for infinity using the main shim and then set the close focus usib=ng the other shim and then check in between. I must emphasis that this last bit is based a little on supposition and as yet I haven't had to do this adjustment. The last J9 i did and is the one offered for sale has been setup this way and the focus ona Bessa R is film tested at infinity and at about 8 feet.
One of these days, I will get round to writing it all up and playing with a J9 to prove or disprove it all. However, It won't be for the next couple of days. I have just received a call from the mail room and the Canon VI-L appears to have just arrived so I am going to take a couple a repair/tinkering free days to go and play with it 😀 😀 😀 😀
