I remember at gun shows & Sportsman shows A salesman from World Optical Products selling anti fog for Rifle scopes, eyeglasses, optics etc... It came in a clear container ( was blue green color) Any one wearing glasses would get a free demo. I bought some, it works well. One container should last a lifetime, have never tried it on camera lens, but plan on it now, to field test it. There are many similar products on the market I haven't tried Parker's anti fog/cleaner, Kleer vu Anti fog.