Fujifilm xf 500mm f 5 6 r lm ois wr vs fujifilm 400mm f 4 5?

Here is what the site says about that.

From Fujifilm XF 500mm f/5.6 R LM OIS WR: Fujifilm XF 500mm f/5.6 R LM OIS WR: A prime lens by Fujifilm for APS-C cameras, 500mm f/5.6. A comparatively light super-telephoto prime, about 750mm equivalent. Specs - Maker: Fujifilm - Focal length: 500mm (prime) - Maximum aperture: f/5.6 - Made for: APS-C sensors - Mounts: Fujifilm X - Stabilised: yes - Autofocus: yes What it frames like - On APS-C (Fujifilm X): like 750mm on full frame; f/5.6 gives about the depth of field of f/8.4 there. ...

From Fujifilm XF 100-400mm f/4.5-5.6 R LM OIS WR: Fujifilm XF 100-400mm f/4.5-5.6 R LM OIS WR: A zoom lens by Fujifilm for APS-C cameras, 100-400mm f/4.5-5.6.

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