When light hits a glass surface not all of it passes through to the other side, some of it is reflected back off the lens surface and because of this, some of the light that would have traveled to the viewer’s eye is lost. This light loss occurs anywhere there is lens to air contact. An uncoated lens can lose around four percent of the light it comes in contact with. The more lenses in a scope, the more light is lost. Read more here - http://tacticalted.com/blog
Edited by TacticalTed.com, 23 September 2014 - 07:01 AM.