Many people ask me what is the purpose of mirror coating on Sunglasses. Some people think it’s only cosmetic. It does have a job to do. The main job of mirror coating is to reflect harsh light rays from the eyes. Consider it as a wall that light must pass to cause your eyes fatigue from the strong sun. It is recommended for extremely bright light conditions. Many brands such as Julbo will apply it to their glacier sunglasses models for the glare from the snow. Manufacturers will offer solid and flash mirror coatings. You can even see gradient mirror coating on occasions. Solid mirror coating is applied fully to the whole lens and other people can see their reflection in it. Flash mirror coating is partially applied to the lens and does not have the full mirror effect. This produces a shiny effect to the lens surface. Gradient mirror coating can be present when the mirror coating fades in the middle of the lens and completely disappears at the bottom. People can still see your eyes through a flash mirror coating.
I will be completely honest, I like mirror coating for a very different, very useful reason. When I am at the beach or walking around shopping on a weekend afternoon I use my mirror coating to people watch without being detected. It allows me to check out attractive people undetected. I have had customer’s request mirror coating for that reason too. One man even joked that he didn’t want to get slapped while checking out pretty girls. So you see mirror coating does a useful purpose, to block bright light and watch attractive people. I won’t get caught peeping while wearing my undercover mirror coating.