Is the pentax hd fa 77mm f 1 8 limited sharp wide open?

Here is what the site says about that.

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. Specs - Maker: Pentax - Focal length: 77mm (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, 77mm. - On APS-C (Pentax K): like 116mm on ...

From Lenses: Aperture: The f-number says how wide the lens opens. Smaller numbers let in more light: f/1.8 lets in about ten times as much light as f/5.6, more than three stops. A wide aperture means faster shutter speeds in dim light and more background blur. Zooms with a constant aperture, like a 24-70mm f/2.8, keep the same exposure throughout the zoom range; cheaper zooms get darker as you zoom in.

Quoted from this site's pages.