HD Pentax-D FA 15-30mm F2.8 ED SDM WR
Bokeh
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 blades. Their number and shape will influence the look of the bokeh, especially around highlights and light sources.
The Pentax 15-30mm features 9 curved aperture blades, which should offer superb results regarding bokeh. Wider lenses offer longer depths of field, so backgrounds are less visibly blurred, which could counterbalance this to some extent.
Bokeh Test
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.
| Pentax at 30mm | |
| F2.8 |  |
| F4 |  |
| F5.6 |  |
| F8 |  |
| F11 |  |
| F16 |  |
| F22 |  |
The out of focus areas are pleasantly rendered. Textures appear smooth, highlights are beautifully rounded. Especially at wider apertures, there are no harsh transitions to be seen, even with a busy scene.
The out-of-focus range of course gets thinner when the aperture closes but the blurred zones still preserve their smooth texture.
Verdict
The 15-30mm produces pleasing bokeh, certainly above expectations for a zoom and a wide lens.
Further examples of the performance of this Pentax lens can be found in the sample gallery near the end of this review.
