Pentax smc da 50mm f 1 8 vs pentax smc da 55mm f 1 4 sdm?

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From Pentax smc DA* 55mm f/1.4 SDM: Pentax smc DA* 55mm f/1.4 SDM: A prime lens by Pentax for APS-C cameras, 55mm f/1.4. Specs - Maker: Pentax - Focal length: 55mm (prime) - Maximum aperture: f/1.4 - Made for: APS-C sensors - Mounts: Pentax K - Stabilised: no - Autofocus: yes What it frames like - On APS-C (Pentax K): like 82mm on full frame; f/1.4 gives about the depth of field of f/2.1 there. - On the larger-sensor bodies of Pentax K: ...

From Pentax smc DA 50mm f/1.8: Pentax smc DA 50mm f/1.8: A prime lens by Pentax for APS-C cameras, 50mm f/1.8. The cheapest fast portrait lens for Pentax APS-C bodies. Specs - Maker: Pentax - Focal length: 50mm (prime) - Maximum aperture: f/1.8 - Made for: APS-C sensors - Mounts: Pentax K - Stabilised: no - Autofocus: yes What it frames like - On APS-C (Pentax K): like 75mm on full frame; f/1.8 gives about the depth of field of f/2.7 ...

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