Sony E 18-55 mm f/3.5-5.6 OSS
7. Coma and astigmatism
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The coma is corrected equally well at all focal lengths and you can notice it only at the widest angle. Even at 18 mm and wide open its level is acceptable. The lens fares very well here and it gets a positive mark.
The astigmatism mark is worse because the tested lens belongs to the NEX system with currently only one sensor available - that used in the NEX-3 and NEX-5 cameras. The test of the latter showed the difference between the horizontal and vertical resolution amounting to 15-20% for two lenses. It is difficult to say explicitly whether these two lenses really feature such a similar astigmatism level; perhaps (and it is a more probable assumption) it’s the sensor and the low-pass filter which cause such asymmetry. A more insightful astigmatism analysis at different combination of apertures and focal lengths only allows us to say that in the middle of the focal range the astigmatism of the tested kit cannot be passed over. At both ends of focal range the influence of astigmatism is certainly weaker and the differences in resolution are more due to the properties of the sensor.
