Coating of lenses

Up to 4% of light entering the binoculars bounce off the lens surfaces in stead off proceeding towards the exit pupil, which is bad for the clarity of the image. This can be prevented by covering the lenses with anti-reflective coats (usually magnesium fluoride), which will enhance the quality of the image. More sophisticated multi-coatings of 7 to 15 layers further reduce reflected light and can result in total light transmission through a lens or prism of 99% or more.
These coating differ substantially in quality: “Coated” simply means a single layer anti-reflection coating on the two objective lenses; “Fully coated” means that all air-to-glass surfaces are coated, whereas the ideal coating, “fully multi-coated” means all air-to-glass surfaces have multiple layers of coats.

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