Is the sony fe 400mm f 4 5 gm oss long enough for birds?

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From Sony FE 400mm f/4.5 GM OSS: Sony FE 400mm f/4.5 GM OSS: A prime lens by Sony for Full frame cameras, 400mm f/4.5. A 400mm prime of about a kilogram, light enough to hand-hold. Specs - Maker: Sony - Focal length: 400mm (prime) - Maximum aperture: f/4.5 - Made for: Full frame sensors - Mounts: Sony E - Stabilised: yes - Autofocus: yes What it frames like - On full frame (Sony E): as marked, 400mm. - On APS-C (Sony E): like ...

From Sony FE 100-400mm f/4.5-5.6 GM OSS: Sony FE 100-400mm f/4.5-5.6 GM OSS: A zoom lens by Sony for Full frame cameras, 100-400mm f/4.5-5.6.

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