28mm repaired.

I decided that I could not justify the cost of professional cleaning, so I would attempt to repair the lens myself. For cleaning I just undid the 4 external screws that secured the mount and then unscrewed the back lens assembly by hand. I wet a cotton "ear bud" with methylated spirits and cleaned the aperture with a circular motion (following the iris ridges). then ran a dry bud over the aperture to clean. I opened and closed the aperture about 20 times during the process to distribute the metho. I was very careful to keep the iris vertical so that if I did have an accident, nothing could drip onto the lens.
I had to repeat the process three times letting the assembly air dry for about 10 minutes between cleaning. It was important to let the aperture dry before checking the stiffness because the dampness of the metho made the iris stick a little bit.
I should point out that I have opened lots of lenses in the last couple of years (and destroyed a few in the process). This was a simple fix, but if you have never opened a lens before, I recommend you get some practice first.


It worked! Finally the iris movement was like a feather! I reassembled and confirmed everything was working as expected. Here are a few sample shots...