Before revision: This lens is selected in such a way that the maximum visual acuity lies on the font sight line element near the muzzle of the (non-magnifying) open type or diopter and globe type match sight line elements .Shooting Glasses for Pistol, Rifle and Archery, By Barry Nolt This is necessary because the shooter can influence the weapon and sight line elements and not the target.
After revision: to get three points positioned in three different optical planes in acceptably sharp focusThis lens is selected in such a way that the maximum visual acuity lies on the font sight line element near the muzzle of the (non-magnifying) open type or diopter and globe type match sight line elements .Shooting Glasses for Pistol, Rifle and Archery, By Barry Nolt This is necessary because the shooter can influence the weapon and sight line elements and not the target.