Overview

The Sigma 400mm f/5.6 APO is a vintage telephoto lens from the 1990s, offering good sharpness wide open but with notable weaknesses: difficult manual focus, persistent purple/pink chromatic aberration in harsh light, and a sliding lens hood. It is reasonably compact and lightweight for a 400mm lens, with a close-focus capability of 1.6m giving 1:3 magnification. It suits budget-conscious wildlife or sports photographers willing to work around its quirks, but may frustrate those seeking consistent results.