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Lens review

Sony Carl Zeiss Vario Sonnar 16-35 mm f/2.8 T* SSM

4 August 2009
Arkadiusz Olech

7. Coma and astigmatism


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When writing about coma you can have mixed feelings. On the one hand, the lens should be praised for good frame corner coma correction on the smaller sensor. The aberration is practically imperceptible there and the diode keeps its circular shape. When we proceed to the full frame corner results, though, the situation changes completely. The coma influence is clearly visible there at all focal lengths, starting with a really enormous level at 16 mm through a quite big level at 24 mm and ending with still significant level at 35 mm.

Sony Carl Zeiss Vario Sonnar 16-35 mm f/2.8 T* SSM - Coma and astigmatism

At the end of the focal lengths range the astigmatism, understood as an average difference between the vertical and horizontal MTF50 function values, reached virtually imperceptible level of 5%. What’s interesting, in the middle of the range the astigmatism increased to 11%. Perhaps exactly this off-axis aberration is the reason why there’s no continual resolution increase after stopping the lens down to f/5.6 – we discussed it in the image resolution chapter.