Pentax 50mm Prime Lens Shootout
Bokeh is Japanese for blur, or the aesthetic quality of the blur, in a photograph. A lens is said to produce good bokeh if the blurred pattern is pleasing to the eye. Conversely a lens that produces bad bokeh is said to have a harsh or coarse blur pattern. Bokeh is produced in part by the lens design. The shape and number of blades in the aperture does not always determine if the lens produces good or bad bokeh. However, the number of blades determines the shape of the out-of-focus highlights.
The Pentax D FA 50mm F2.8 Macro and the FA 50 F1.4 have eight aperture blades; the DA 50 F1.8 has seven blades. Since the D FA Macro and FA have more blades, the highlights should be more circular that those of the DA. None of these lenses have circular blades, however, so at times you may be able to make out some jagged edges in the bokeh.
The winner was the FA 50mm F1.4 lens, but the DA 50mm F1.8 was a close second, and of course that makes the D FA 50mm F2.8 third. The bokeh, of all the three lenses reviewed, is very creamy but we believe that the FA 50 F1.4 presents better bokeh.