Nikon Nikkor AF-S 70-200 mm f/2.8G IF-ED VR
7. Coma and astigmatism
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Generally the coma doesn’t make itself felt but if you look at the image of the diode in the frame corner at 130 mm you can notice a distinct deformation; it partially explains weaker achievements of this lens at that focal length and wide open. Fortunately at other focal lengths and after attaching the converter, the situation is much better.
If you use only the lens, the second of off-axis aberrations – the astigmatism - won’t be bothersome at all. Its average level remains low, amounting to 4.5%. You can also notice a tendency here – in the 70-130 mm range the astigmatism is practically zero but at 200 mm it increases sharply to over 7%. The worst situation we have after attaching the converter, though. The additional optical element means additional links and threads – all of them make the level of this aberration increase to as much as 18%. Nothing to boast of, to be sure…
