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A history of Sony Alpha - Minolta AF 85 mm f/1.4 G D versus Sony Zeiss Planar T* 85 mm f/1.4

22 December 2009
Szymon Starczewski

7. Coma and astigmatism

The spot diode was put in the frame centre, in the APS-C sensor corner and in the full frame sensor corner. The relevant pictures crops are presented below.

Minolta AF 85 mm f/1.4 G D
A history of Sony Alpha - Minolta AF 85 mm f/1.4 G D versus Sony Zeiss Planar T* 85 mm f/1.4 - Coma and astigmatism
Zeiss Planar T* 85 mm f/1.4
A history of Sony Alpha - Minolta AF 85 mm f/1.4 G D versus Sony Zeiss Planar T* 85 mm f/1.4 - Coma and astigmatism


The first thing that sticks out is not coma but rather the Minolta’s astigmatism; amounting to 16%, it doesn’t allow to get a spot picture of the diode, as it was in the case of the Sony, which astigmatism at the level of 9% is lower. A higher level of astigmatism for an older lens shouldn’t surprise us at all because, as the time goes by, this aberration has a tendency to increase due to slight operating slacks in the casing and by elements shift. On the other hand, though, the G series was the best and the most expensive Minolta lenses series and it was supposed to be designed to withstand years of intensive wear and tear.


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Returning to the coma, we could write that also in this category the Sony performs better. In the APS-C sensor corner the coma problem practically doesn’t exist in both cases, although if you look closely the Minolta’s result seems to be a tad worse. In the full frame corner there’s no doubt that the Sony fares better.