Is the pentax hd fa 31mm f 1 8 limited good in low light?

Here is what the site says about that.

From Pentax HD FA 31mm f/1.8 Limited: Pentax HD FA 31mm f/1.8 Limited: A prime lens by Pentax for Full frame cameras, 31mm f/1.8. Same optics as the earlier smc FA 31mm Limited. Specs - Maker: Pentax - Focal length: 31mm (prime) - Maximum aperture: f/1.8 - Made for: Full frame sensors - Mounts: Pentax K - Stabilised: no - Autofocus: yes What it frames like - On full frame (Pentax K): as marked, 31mm. - On APS-C (Pentax K): like 46mm on ...

From Pentax HD FA 77mm f/1.8 Limited: Pentax HD FA 77mm f/1.8 Limited: A prime lens by Pentax for Full frame cameras, 77mm f/1.8. Same optics as the earlier smc FA 77mm Limited.

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