Sigma's earlier 500mm for Nikon — the f/4.5 EX APO without OS, same as ID 4098.
The Sigma 500mm f/4.5 EX APO DG is a professional super-telephoto prime from Sigma's EX line for Nikon F full-frame bodies, providing extreme reach at a bright f/4.5 maximum aperture. APO apochromatic glass controls chromatic aberration at this extreme focal length.
The lens delivers 500mm at f/4.5 maximum aperture with APO glass, EX professional build quality, DG full-frame coverage, and Nikon F-mount AF coupling. Physical dimensions and weight require tripod or monopod support.
The 500mm f/4.5 provides substantially less light gathering than a 500mm f/4 (half a stop) but correspondingly more compact dimensions and lower weight. Used for professional wildlife and sports photography at distances requiring extreme telephoto reach with faster-than-f/5.6 aperture.
Test autofocus tracking speed at maximum aperture. Verify APO glass condition. Check tripod collar rotation. Inspect the large front element. Compare AF performance against body-integrated AF systems for tracking accuracy.