What are the alternatives to the leica elmarit m 21mm f 2 8 asph?

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From Leica Elmarit-M 21mm f/2.8 ASPH: Leica Elmarit-M 21mm f/2.8 ASPH: A prime lens by Leica for Full frame cameras, 21mm f/2.8. Specs - Maker: Leica - Focal length: 21mm (prime) - Maximum aperture: f/2.8 - Made for: Full frame sensors - Mounts: Leica M - Stabilised: no - Autofocus: no, manual focus What it frames like - On full frame (Leica M): as marked, 21mm. Cameras it fits - Leica M9: Full frame - Leica M9-P: Full frame - [Leica ...

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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