Take one look through a binocular or spotting scope equipped with ED glass, and you’ll immediately notice the vivid, lifelike color and razor-sharp images. But what exactly gives ED glass its signature look?
ED stands for "extra-low dispersion," which refers to the composition and optical properties of the glass used for the lenses. ED glass is specially formulated and contains rare-earth compounds that greatly reduce a visual defect called chromatic aberration. Also known as “color fringing,” chromatic aberration occurs when the wavelengths for different colors of light do not converge on the same focal plane. It’s most apparent when viewing light colored objects on a dark colored background and looks like an unnatural “halo” effect that softens the focus of the overall image.
