Lens Coating
The coatings on the lenses and prisms of any optic are as important to a clear, bright and sharp view as any other factor. Good coating schemes in an optic will determine how well it performs. Light reflects off lens surfaces both destroying image clarity and brightness. Light transmission may vary from 95% in good optics down to 50% in poor optics. Full descriptive text on how these are defined and how they effect your view can be found in the Basics IV article in the All About Optics section.