High-grade glass offers a more clear, vivid image than standard glass
The optical glass used in a binocular affects the quality of the image you see through it. The objective lens of a binocular refracts or bends light, directing it to a focal point at some distance behind the lens of the binocular. Each color or frequency within the visible light spectrum has certain characteristics. As light passes through the lens, each color bends at a slightly different angle and focuses at different points, causing a reduction of color fidelity that degrades image sharpness and overall optical quality. Alpha-class binoculars incorporate special cost- and labor- intensive glass in the optical system to correct chromatic aberration (color fringing). You'll hear about ED (extra-low dispersion) and HD (high definition) glass. When used in binoculars, this type of glass will provide highly resolved images with enhanced brilliance and true color.