The lining on the inside of the tripod collar for my Canon 300mm f/4 L lens was causing problems. It has partially disintegrated and was smeared on the outside of the lens, and due to the accumulated gunk, the lens no longer turned smoothly in the collar. I sought advice on the EOS email list and got a good solution. Album includes before and after photos of the inside of the collar and the lens.
Album was created 7 years 2 months ago and modified 2 years 2 months ago