- br br Bargain Review - Pentax Fixed 55mm f 2.8 Standard Lens for Pentax 645Dbr br Fixed 55mm f2.8 lens designed for the Pentax 645Dbr Fully weather sealed design to work with the weather sealed 645D.br Quiet SDM autofocus motro provides fsta and accurate autofocus operation.br Curved aperture blades provide a circular aperture at f5.6 for extremely smooth image bokeh.br Pentaxt quick shift autofocus instantly shifts from auto to manual focus for on the fly focus accuracy.