It is lens coatings that turned both riflescopes and binoculars into practical tools for hunting and shooting. Before coatings, light transmission severely limited the practical use of both.

With enough lenses between the eye and a target, the target could essentially be reflected away to nothing. Magnesium fluoride (MgF) is a simple, widely used single-coating material that greatly reduces the amount of light reflected by a lens. The compound's refractive index--the measure of how much the speed of light is reduced in a given medium--falls between the refractive index of air and glass, giving it the physical properties it needs to reduce reflections by nearly 50 percent, reducing light loss to just two percent per lens surface.

"Leupold has different coatings spanning from very simple MgF to Multicoat and Multicoat 4 to index-matched broadband AR to XTended Twilight with DiamondCoat 2," Smith said. "As you move from MgF up the scale, you tend to get better light transmission across the visible spectrum, which appears to your eye as a brighter, crisper, and more accurate optic."

Adding multiple coatings allows lens makers to fine tune portions of the visible light spectrum, but they have to keep in mind the refractive index of each layer and keep a running total of the combined index of the layers or the equation quickly unhinges. They control the refractive index through layer thickness--measured in nanometers--of that particular layer.

Using certain types of glass with certain coatings could produce unnatural tints, at least to the human eye. Though pure, perfect colors are usually more important to camera lens manufacturers, optic makers can adjust the coating to increase or decrease the amount of light in the specific area of the light spectrum to correct unnatural tinting. The end user sees not only a lot of light, but the correct color of light as well. Some scope makers have introduced coatings that increase the contrast between certain colors, like the brown of animal fur and the green of tree leaves, to give hunters searching for game a small edge.

Leupold's more advanced coatings alternate layers of metal oxides, like aluminum oxide, titanium oxide, and silicon oxide. Each oxide manipulates a specific wavelength of light. The layers work in concert, producing a better coating, and less reflectance is achieved. Really good coatings can reduce the amount of reflected light loss to less than 0.5 percent per lens surface--an amazing accomplishment. No scope, no matter how good, can transmit 100 percent of the light through all its elements--it would simply defy the laws of physics. There is also a small amount of light absorption that occurs with any glass, although this is usually on the order of 0.1 percent per lens or less.