Is the pentax smc da 40mm f 2 8 xs worth buying used?

Here is what the site says about that.

From Pentax smc DA 40mm f/2.8 XS: Pentax smc DA 40mm f/2.8 XS: A prime lens by Pentax for APS-C cameras, 40mm f/2.8. An ultra-thin pancake, even slimmer than the 40mm Limited. Specs - Maker: Pentax - Focal length: 40mm (prime) - Maximum aperture: f/2.8 - Made for: APS-C sensors - Mounts: Pentax K - Stabilised: no - Autofocus: yes What it frames like - On APS-C (Pentax K): like 60mm on full frame; f/2.8 gives about the depth of field of f/4.2 ...

From Buying used: Buying used: Cameras and lenses are built to last, and many photographers upgrade often. That makes the used market one of the best ways to afford good gear. A body that's one or two generations old is often most of the camera for a fraction of the price.

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