HD Pentax-D FA* 70-200mm F2.8 ED DC AW

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 70-200mm features 9 curved aperture blades, which should offer superb results regarding bokeh. The Tamron also has 9 blades, although they are not curved. This might be visible at wider apertures, something our tests will show. 

Bokeh Test

In order to evaluate the characteristics of the background blur, we took pictures at varying apertures, using these test parameters:

  • Tripod
  • 2s Timer
  • Focal Length: 200mm
  • Camera: K-1
  • Camera Mode: Aperture priority
  • Shutter Speed: Set relative to aperture
  • ISO: 100
  • Distance to subject: 5 meters

Results are directly transferable to APS-C cameras.

The scene is a field of leaves, purposefully defocused. Both lenses are compared with the same scene. Click on the images to see larger versions.

Pentax at 200mm Tamron at 200mm
F2.8 Pentax F2.8 Tamron F2.8
F4 Pentax F4 Tamron F4
F5.6 Pentax F5.6 Tamron F5.6
F8 Pentax F8 Tamron F8
F11 Pentax F11 Tamron F11
F16 Pentax F16 Tamron F16
F22 Pentax F22 Tamron F22

Our two test lenses perform almost identically for this test. One would be hard-pressed to identify which is which by performing a blind comparison. And this is good news. In both cases, the out-of-focus blur is smooth, even, and free of strong distracting highlights. Even when closed down, the bokeh retains most of its smoothness, and allows a good separation from the foreground.

It is clear that, in this case, the number of aperture blades contributes more to the bokeh's appearance than the shape of the blades.

Verdict

Both lenses perform very well regarding bokeh, especially considering that they are zooms. At all apertures, bokeh is pleasing and devoid of distracting highlights. This will be desirable for many shooting situations, such as portraits and weddings.

Further examples of the performance of the Pentax lens can be found in the sample gallery near the end of this review.


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