Is the pentax hd d fa 21mm f 2 4 ed limited dc wr worth buying used?

Here is what the site says about that.

From Pentax HD D FA 21mm f/2.4 ED Limited DC WR: Pentax HD D FA 21mm f/2.4 ED Limited DC WR: A prime lens by Pentax for Full frame cameras, 21mm f/2.4. A compact, weather-sealed wide prime for the full-frame bodies. Specs - Maker: Pentax - Focal length: 21mm (prime) - Maximum aperture: f/2.4 - Made for: Full frame sensors - Mounts: Pentax K - Stabilised: no - Autofocus: yes What it frames like - On full frame (Pentax K): as marked, 21mm. - On APS-C (Pentax K): like 32mm on ...

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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