Sigma 70-300 mm f/4-5.6 DG OS
7. Coma and astigmatism
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The coma is noticeable only at the shortest focal length. On passing to the 135-200 mm range this aberration decreases significantly and it disappears practically at 300 mm. The lens’s performance can be assessed as positive then.
When it comes to the astigmatism the results are at medium level. On the smaller Nikon’s D200 sensor the average difference between vertical and horizontal MTF50 function values amounted to 9%. On full frame that value increased to 13%, most probably because the measurement areas and the optical axis of the lens were further apart.
