Sony fe 400 800mm f 6 3 8 g oss vs sigma 300 600mm f 4 dg os sports?

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From Sony FE 400-800mm f/6.3-8 G OSS: Sony FE 400-800mm f/6.3-8 G OSS: A zoom lens by Sony for Full frame cameras, 400-800mm f/6.3-8. Sony's longest zoom, for birds and distant wildlife. Specs - Maker: Sony - Focal length: 400-800mm (zoom) - Maximum aperture: f/6.3-8 (it gets darker as you zoom in) - Made for: Full frame sensors - Mounts: Sony E - Stabilised: yes - Autofocus: yes What it frames like - On full frame (Sony E): as marked, 400-800mm. - On ...

From Sigma 300-600mm f/4 DG OS Sports: Sigma 300-600mm f/4 DG OS Sports: A zoom lens by Sigma for Full frame cameras, 300-600mm f/4. A constant f/4 super-telephoto zoom for wildlife and sport. Specs - Maker: Sigma - Focal length: 300-600mm (zoom) - Maximum aperture: f/4 - Made for: Full frame sensors - Mounts: Sony E, L-Mount - Stabilised: yes - Autofocus: yes What it frames like - On full frame (Sony E, L-Mount): as marked, 300-600mm. - On APS-C (Sony E, L-Mount): ...

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