Pentax 50mm F1.4 comparison: M, FA and DFA
Bokeh is a Japanese term which refers to the quality, look and texture of the background blur. It does not relate to the depth of field but to the areas in the image that are beyond the range that is expected to be in focus.
A smoother bokeh is generally perceived as being of a higher quality. Bokeh is influenced by the lens design, with a significant role being played by the aperture. Its shape will influence the look of the bokeh, especially around highlights and light sources.
Modern lenses generally produce pleasing bokeh since this element is often sought after by buyers. The three tested lenses' fast, F1.4 maximum aperture should help with the out of focus rendering, as should their rounded aperture blades in some cases.
In order to evaluate the characteristics of the background blur, we took pictures at varying apertures, using these test parameters:
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Results are directly transferable to APS-C cameras.
|M 50mm||FA 50mm||DFA* 50mm|
Wide open, there is little to differentiate the three lenses. The texture produced by the D FA* is a bit creamier, but the difference isn't all that significant. Even at F2, the M 50mm's highlights take on an octagonal shape. The same happens with the FA 50mm at F2.8. Textures are more strongly defined as the aperture closes with the M lens, and to a lesser extent with the FA. Meanwhile, the D FA* retains round highlights and a smoother out-of-focus blur.
More examples can be found in our Samples Gallery.
The D FA* again steals the show. While there is little to distinguish the three lenses wide open, as the aperture closes the newer lens produces more rounded highlights smoother textures. The FA performs a bit better than the M. Truth be said, however, all three lenses are excellent performers regarding bokeh.