The FE 400mm f/4.5 G Master OSS is Sony’s long-awaited answer to the über-popular Nikon Nikkor Z 400mm f/4.5 VR S lightweight telephoto lens. Alongside the new FE 600mm f/6.3 GM OSS, the 400mm f/4.5 is also Sony’s first alternative to the Sigma 500mm f/5.6 DG DN Sports. Is the 400mm f/4.5 a strong answer to the competition?