Sony DT 16-50 mm f/2.8 SSM review - Coma, astigmatism and bokeh

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Sony DT 16-50 mm f/2.8 SSM

25 April 2012

Arkadiusz Olech

7. Coma, astigmatism and bokeh

As you can notice in the crops below the coma is not a big problem of the tested lens although its influence on the shape of a diode, positioned in the corner of the frame, is visible at every focal length. This aberration seems to increase slowly with the increase of the focal length, being low at 16 mm but reaching medium level at 50 mm.

Sony DT 16-50 mm f/2.8 SSM - Coma, astigmatism and bokeh

When it comes to the astigmatism it is corrected better than the coma. The average difference between horizontal and vertical MTF50 function values amounted to just 3.3% which is very good, praiseworthy result.

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The crops below show defocused diode images taken from the centre and the corner of the frame. It is clear that the light in the circle is more or less evenly spread and only on the very edge there is a distinct rim. What’s interesting, when you pass to the other side of the focus that rim gets significantly less intensive. You can expect that the blur before the object itself will look better than that from the background behind the object you set the focus on.