Actually, the phrase "dielectric coatings" has a very specific meaning in this case ans has little to do with marketing.
Traditional reflective coatings used on the roof prisms (one of the surfaces, to be exact), were made of metal: either aluminum or silver. Newer multilayer coatings are typically made out of multiple alternating layers of two (or more depending on the purpose) dielectric materials. The specific materials vary, but typically these are various metal oxides and salts like TiO2, MgF2, CaF and various vanadium oxides among others. These materials are dielectrics and the original term was used to differentiate them from older style deposited metal coatings.
Also, to address a comment from somewhere earlier in the thread, Vortex Viper and Razor binoculars switched to dielectric coatings a bit over a year ago, I think.
ILya
Last edited by koshkin; 11/24/10.
