What is the zeiss batis 40mm f 2 cf good for?

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From Zeiss Batis 40mm f/2 CF: Zeiss Batis 40mm f/2 CF: A prime lens by Zeiss for Full frame cameras, 40mm f/2. Specs - Maker: Zeiss - Focal length: 40mm (prime) - Maximum aperture: f/2 - Made for: Full frame sensors - Mounts: Sony E - Stabilised: no - Autofocus: yes What it frames like - On full frame (Sony E): as marked, 40mm. - On APS-C (Sony E): like 60mm on full frame; f/2 gives about the depth of field ...

From Focal length converter: Aperture and depth of field: The f-number sets exposure, and that doesn't change with sensor size: f/2.8 gives the same brightness on a phone as on medium format. Depth of field does change. At the same framing, multiply the f-number by the crop factor to get the full-frame aperture with the same depth of field: f/1.8 on APS-C gives about the background blur of f/2.7 on full frame, and f/1.8 on Micro Four Thirds about ...

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