When you clean ANY lens, with ANY method, you WILL lose "some of the coating". Anything that comes in contact with the coating, including liquids, will abrade and remove some of it. In the interest of preservation - NOT cleaning the lens , it is good advice to mount a filter on the lens - "UV" or "Skylight" or some other such "clear filter" - and leave it there. You can go crazy cleaning the filter - if you like, and just replace the filter after it is completely opaque.Originally Posted by firecracker
In a different life, I was a Quality Assurance Specialist in a large company producing sophisticated optical systems. We were allowed ONE method to clean lenses: Distilled water and surgical cotton -- with NO pressure. If whatever foreign material could not be removed, the lens was sent to Technicians SPECIALIZING in lens cleaning. We had one really unfortunate instance involving the use of a common pencil eraser - I've never seen anyone fired so quickly in my life.
However, you mention "fog". What is usually seen on the outside of the lens is dust. Are you sure that "fog" is on an external lens surface? If it is internal, it is probably fungus, and your one hope is to have it disassembled, cleaned and if necessary, re-coated.... not an inexpensive task.
Your best bet there would be to contact Schneider USA, and talk to them.