An easy-to-use viewing and focusing aid which allows near and farsighted photographers to view the finder image accurately without wearing eyeglasses. The optional Nikon dioptre correction eyepiece allows you to optimize your SLR viewfinder’s sharpness in conjunction with your individual eyesight. The dioptre correction eyepieces are designed for specific camera models and are identified by a plus, a minus or a neutral numeric dioptre value.