Grasp the focus ring, and GENTLY and VERY SLOWLY turn it CLOCKWISE. After removing the anti-rotation pinions, it will begin to unscrew from the focus helicoid. At one point it will came loose. MARK WITH THE MAXIMUM PRECISION THAT POINT ON BOTH THE RING AND THE BARREL, this time making a little carving with the tip of a screwdriver (obviously not on the helicoid itself). You really DON'T WANT to miss that point. If you miss the marking you will loose focus at the infinity... and the only way to get it again would be by trial and error, dismantling and remounting the lens a number of times equal to the number of entry points in the helicoid (and they are typically A LOT)...
From now on, it's also time to clean. Remove the old grease and crud with paper towels and lighter fluid, alcohol or something like that. Take your time, and take care not to smear the exposed lenses. When the helicoid is clean, wash your hands. Then take the most suitable spanner, and VERY CAREFULLY unscrew the rear lens assembly (some force is involved... if you don't feel comfortable protect the lens with a soft cloth... but this step IS dangerous. Please be careful and DON'T SCRATCH your rear lens assembly!)
[This step is required only to thoroughly clean the rear lens assembly. If yours is not to be cleaned, leave it as it is.]
Put the lens assembly away, and DO NOT LAY IT ON A HARD SURFACE.
Now that the most exposed part of this phase is safely stored away, we can clean some more and relax a bit. The tricky parts have yet to come...
On a side, near the focus helicoid, you will find a very small hole, with the smallest screw of your life hidden inside. Unscrew it with a suitable precision screwdriver, WITHOUT TAKING IT COMPLETELY OUT. If it exits that hole, it will require an extra amount of time to be reinserted... and remember that screws of that ridiculous diameter are really easy to mangle...
Now unscrew the following 'cap' (that was retained by that very small screw):
Page 3/6
