Tokina AT-X 840 AF D 80-400 mm f/4.5-5.6
7. Coma and astigmatism
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The coma, like the distortion, is not an aberration you can complain about. Observing the outstanding resolution performance at 80 mm it would be difficult to expect that the coma would be visible at that focal length. And, according to our expectations, it isn’t. However, it appears with the increase of the focal length, reaching its peak at 400 mm but even there its value remains low.
Unfortunately, we can’t say so many good things about astigmatism. The average difference between vertical and horizontal MTF50 values at all focal lengths amounted to 10%. Once again we saw a growth tendency connected with the increase of the focal length because at 80 mm this aberration is practically invisible and at 400 mm it reaches a very high level of over 15%.
