Canon rf 100 300mm f 2 8l is usm vs sigma 50 120mm f 2 8 dc os contemporary?

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From Canon RF 100-300mm f/2.8L IS USM: Canon RF 100-300mm f/2.8L IS USM: A zoom lens by Canon for Full frame cameras, 100-300mm f/2.8. A professional sport and wildlife zoom that stays at f/2.8 throughout. Specs - Maker: Canon - Focal length: 100-300mm (zoom) - Maximum aperture: f/2.8 - Made for: Full frame sensors - Mounts: Canon RF - Stabilised: yes - Autofocus: yes What it frames like - On full frame (Canon RF): as marked, 100-300mm. - On APS-C (Canon) (Canon RF): ...

From Sigma 50-120mm f/2.8 DC OS Contemporary: Sigma 50-120mm f/2.8 DC OS Contemporary: A zoom lens by Sigma for APS-C cameras, 50-120mm f/2.8. A compact constant f/2.8 telephoto zoom for APS-C, about 75-180mm equivalent. Specs - Maker: Sigma - Focal length: 50-120mm (zoom) - Maximum aperture: f/2.8 - Made for: APS-C sensors - Mounts: Sony E, Fujifilm X, Canon RF - Stabilised: yes - Autofocus: yes What it frames like - On APS-C (Sony E, Fujifilm X): like 75-180mm on full frame; f/2.8 ...

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