Sticky Zenitar aperture blades
some oil on the aperture blades of my Zenitar almost spoiled my WWP shot.
I shot a panorama in a quite dark place and was suprised to have
relatively bright images at short exposure time. When I put off the Lens
I recognized that the aperture wasn't closed as much as it should at
f/16. Some oil on the blades made them stick together. Luckily I could
make them close as much as I wanted turning the aperture ring some times
and redo the shot.
At home I unscrewed the lens (took of the adapter and the rear element
which is hold by three screws. The oil came from the excessive grease
used for the focus screw thread. I had to dismount the whole rear part,
bath the aperture blades in some benzin, clean the other parts and
remove excessive grease. Now it works again perfectly.
To see whether your Zenitar has excessive grease too, you can unscrew
the front part (just the ring which forms the sunshade). This way you
can see the other side of the focus thread. If there is excessive grease
it most likely is on the other side as well. In this case you should
consider removing it, before it reaches the aperture blades.
Although the repair is not very hard you should know what you are doing
and of course have some experience already. Perhaps better you go to a