Good topic. I have a pair of Leitz Trinovid 8 x 20c very compact, nice for carrying. I got them from my father and sent them out for servicing--cleaning, etc as dad had used them fairly hard and they were a bit foggy. They came back only a little brighter. I am wondering if once they get into that condition (maybe from bringing them indoors after being out in the cold) if they can ever be restored to their original clarity.
Gil, perhaps the coatings are worn off, that would cause them to fall off in clarity and cut back on light transmission.
For years I used those "lens pens" that leupold made popular but they just ground dirt into lenses and removed coatings. Now I use comp. air, then cleaner and a lens cloth.
Rob