Why sacrifice high image quality at telephoto ranges? With the 500mm APO you don't have to. SLD glass eliminates chromatic aberration and delivers sharp high-contrast image quality. Focusing works with an internal mechanism so that overall length  and the center of gravity  never changes. Manual focusing can be done with a single finger and shutter opportunities can be grabbed in an instant. It is equipped with front end protective glass. The use of rear insertion-type filters enables rapid, secure filter changes.