Tokina AT-X DX AF 16.5-135 mm f/3.5-5.6
7. Coma and astigmatism
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As you can see in the crops presented below, the coma is quite well corrected only near 35 mm. In other ranges this aberration is visible but, fortunately, not huge. It does contribute to the worsening of the frame edge image quality though.
Astigmatism is something which plagues the Tokina even more. We don’t know whether a significant focusing backlash in the middle of the range makes the optical elements more loosely fitting and their movements - not so precise but, looking at the results in this category, it is quite probable,. The average difference between vertical and horizontal MTF50 function values amounted to 15% here, brushing already against a high level…
