If you've ever looked closely at a high-quality camera lens, a premium pair of binoculars, or the sophisticated optics on an AI sensor, you've seen a subtle, shimmering tint—a faint purple, green, or amber glow. That tint is the signature of an Optical Coating  (or Thin-Film Coating ), and it's the layer that dictates whether your entire optical system works perfectly, or barely works at all. For anyone involved in AI vision, lasers, or advanced sensing , understanding these