I don't know the technical distinction, but there is a noticeable distinction in prcatice. I guess that "cheap coating" is made by gluing a film; I see this type of coating very often in budget or even not-so-budget sports (sun)glasses.
Cleaning this type of glasses in an unltrasonic cleaner will cause bubbles to form between the film and the lens.
I don't know the technical distinction, but there is a noticeable distinction in prcatice. I guess that "cheap coating" is made by gluing a film; I see this type of coating very often in budget or even not-so-budget sports (sun)glasses.
Cleaning this type of glasses in an unltrasonic cleaner will cause bubbles to form between the film and the lens.