Likely the lubrication has gunked up, especially if it is a much older lens. If you put a couple of drops of naptha or Ronsonol around the ring so that it can get down into the helicoil, you can probably dissolve enough of the gunked-up grease to free it.
It won't stay free, though... someone has to take the thing apart and properly lubricate it. But you have to get it free in order to take it apart. If it's a good lens (ie. not a TV camera lens) it's likely worth having a local camera repair shop do a clean and lube. Most of those older C-mount lenses are easy enough to work on that your local tech should have no problem. It's not like working on a modern zoom with a bunch of moving elements that are all coupled together, it's just one element moving in and out. --scott _______________________________________________ FrameWorks mailing list [email protected] https://mailman-mail5.webfaction.com/listinfo/frameworks
