Riflescopes: Lens Coatings

by
posted on June 13, 2017
** When you buy products through the links on our site, we may earn a commission that supports NRA's mission to protect, preserve and defend the Second Amendment. **
optical-coatings.jpg
In any optical system, some light is lost through reflection each time the light passes through a glass-to-air surface. The light loss can be significant in multi-element riflescopes; as much as 50 percent of the light may be lost to reflection as it passes through an uncoated lens system. 

In the 1940s, it was discovered that magnesium flouride coatings on lenses would increase light transmission, color fidelity and image brightness considerably. Today, nearly all modern scopes have coated lenses that transmit from 95 to 99 percent of the light that enters the objective lens.

Coatings such as zinc sulfide and zirconium oxide are used, often in combination with magnesium flouride. A coated lens will appear tinted when viewed from the side. The exact color may vary from blue, green, purple, red or gold. Abrasion-resistant coatings have been developed for the exterior lens surfaces of modern riflescopes. Water-shedding coatings have also been developed.

Various levels of coating can be applied to lenses ranging from a single layer of magnesium flouride on the exterior objective and ocular surfaces, to as many as 15 layers or more on every surface of every lens. Typically, coating layers are only a few ten-thousandths of an inch thick.

  • The term "fully coated" when applied to a riflescope usually means that all lens-to-air surfaces have at least one coating layer. This includes the interior lens systems as well as the exterior. 
  • The term "multi-coated" or "multiple-layer coated" signifies that multiple coating layers have been applied to some, but not all, lens surfaces. Normally, this means that only the outer lens surfaces have been multi-coated. "Fully multi-coated" signifies multiple coatings on all lens-to-air surfaces.

Lower-priced scopes may have from one to five lens-coating layers while more expensive scopes may have as many as 15 or even more. In lower-priced scopes, only the outside surface of the objective (front) and ocular (rear) lenses are coated. Higher-quality scopes have all internal and external lens surfaces multi-coated.

How many layers are enough? That depends on the quality of the lens system and the intended purpose of the scope. Adding more layers of coating rapidly reaches the point of diminishing returns, but on a high-quality scope where maximum light transmission and image fidelity are necessary, 15 layers of coating can be easily justified.

Latest

Americas Rifle Challenge Lede
Americas Rifle Challenge Lede

Kyle Lamb Named Brand Ambassador for NRA America’s Rifle Challenge

"When I heard about the ARC program, its focus on the AR, and the NRA’s desire to provide AR training and ARC competitions, I wanted to be involved."

Y.E.S! NRA Foundation Awards $13,500 in College Scholarships

We're proud to announce the award recipients from the Y.E.S. Class of 2024!

KelTec Named Stage Sponsor for 2025 NRA World Shooting Championship

This year, KelTec will sponsor two competition stages, supplying innovative firearms for both professional and amateur divisions.

Throwback Thursday: Chinese Broomhandle Mausers

History may not always repeat itself, but it sure can rhyme.

Henry Repeating Arms' Guns for Great Causes: Join "Team Keane"!

The famous arms manufacturer donated 50 custom rifles to support a teen newly diagnosed with leukemia.

FREE NRA Hunter Education Online Course Now Available in Louisiana

The NRA developed this free online course with one main goal in mind: to make it easier for new hunters to get into the field.

Interests



Get the best of NRA Family delivered to your inbox.