Without coatings on the optics of binoculars, images would be blurry and lack contrast since light transmission would be poor, glare would become prevalent and light would be lost through internal reflections. A poor, disappointing view would be had by the observer.
It’s easy to find out if your binocular lenses feature a coating: you’ll see an even dark appearance when you peer through the barrels, while the glass will feature a bluish or greenish tint thanks to a layer of magnesium fluoride. If you see a brownish tint, then your optics are coated with calcium fluoride. Both offer the same outcome — they halt the reflection of some wavelengths, allowing more light to enter your eyes through the exit pupils.
Binoculars largely come in two varieties when it comes to coatings: they’re either fully coated or multi-coated. In both versions, all lenses, glass surfaces and prisms feature at least one layer of magnesium fluoride or calcium fluoride. Binoculars with multi-coated optics are the most superior kind you’ll be able to find on the market, with at least one of the surfaces featuring several layers of anti-reflective compounds.