What are the alternatives to the canon rf 1200mm f 8l is usm?

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From Canon RF 1200mm f/8L IS USM: Canon RF 1200mm f/8L IS USM: A prime lens by Canon for Full frame cameras, 1200mm f/8. The longest autofocus lens Canon makes. Specs - Maker: Canon - Focal length: 1200mm (prime) - Maximum aperture: f/8 - Made for: Full frame sensors - Mounts: Canon RF - Stabilised: yes - Autofocus: yes What it frames like - On full frame (Canon RF): as marked, 1200mm. - On APS-C (Canon) (Canon RF): like 1920mm on full frame; ...

From Sensor sizes: The main sizes: - Full frame (36 x 24mm, the size of a 35mm film frame). The reference size: when people quote a focal length "in full-frame terms", this is what they mean. - APS-C (about 23 x 15mm). Crop factor about 1.5x (1.6x on Canon). Most entry and mid-range mirrorless cameras. - Micro Four Thirds (about 17 x 13mm). Crop factor 2x. Small, light systems from OM System and Panasonic. - 1-inch ...

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