Olympic Shooters look like cyborgs, because they’re wearing a lens, a mechanical iris, and a series of blinders:
An eye at rest would rather focus on a distant object than one that is near at hand; focusing on something in the foreground requires effort, and can lead to fatigue. Adding just a touch of lens power (+0.50 diopter, for the opticians in the house) to a sharpshooter’s prescription can help her sighting eye bring her gunsights into focus and keep them there, even as she concentrates on aligning them with the target in the distance.
But the lens presents a tradeoff: Bringing a gun’s sights into sharper focus can make the target go fuzzy. That’s where the blinders and mechanical iris come in.
“Your eye is like a camera lens,” says Tom Gaylord, a competitive air gunner known in sharpshooter circles as the godfather of airguns. And if you were armed with a camera instead of a pistol, bringing the target back into focus would be as simple as narrowing the aperture of your lens. This increases the range of distance within which objects will appear in focus (aka “depth of field,” for the photographers in the house). A greater depth of field means you can hold a target that’s 30 feet away and a pair of gunsights hovering at arm’s length in focus all at the same time.
A shooter typically mounts his mechanical iris to his shooting glasses just behind his lens. This lets him control the depth of field of his own vision. Twisting the iris narrows its aperture and reduces the amount of light that reaches the shooting eye, bringing the target and both sites into sharper focus than would be possible without the glasses. “The less light you can tolerate, the greater your depth of view will be,” Gaylord says. (Ever tried the pinhole trick, or squinted to see your alarm clock? This setup works by the same principle.)
The blinders serve a similar purpose by reducing the amount of light entering the shooter’s pupils. But the opaque plastic tiles also work to obscure the movements of other shooters and visuals that might otherwise distract an athlete. “I use them to block the vision of my non dominant eye,” says Jason Turner, a three-time Olympic marksman.