Lens review
2010-02-10
Sigma 17-70 mm f/2.8-4.0 DC Macro OS HSM
7. Coma and astigmatism
The coma correction level is quite good. Admittedly its influence on the image quality can be seen at the shortest focal lengths but even there the image of the diode is not deformed significantly. At 50-70 mm the situation is already much improved. For a lens with such parameters and coming from such a price segment these results are nothing to complain about.
Astigmatism won’t cause us practically any troubles. The average difference between horizontal and vertical MTF50 function values amounts to 4.2% which is a very good result.
