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Lens review

Sigma 105 mm f/2.8 EX DG Macro

5 May 2010
Arkadiusz Olech

7. Coma and astigmatism


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The high image quality at the edge of the field stops being a mystery when we look closely at such off-axis aberrations as coma and astigmatism. The first is corrected in a practically perfect manner as it is shown in the picture below.

Sigma 105 mm f/2.8 EX DG Macro - Coma and astigmatism

With the astigmatism we see the same story. Near maximum relative aperture the average difference between vertical and horizontal MTF50 function values amounted to just 5.7%. It’s worth adding here that so far we’ve seen just few lenses which managed to go below 5% in this category.