Canon EF-S 18-200 mm f/3.5-5.6 IS
7. Coma and astigmatism
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The coma looks very similar at all focal lengths and isn’t very bothersome. Its influence on the shape of the diode is slight although still noticeable if you examine the photos more closely.
At longer focal lengths the astigmatism is medium at most because its value we assessed as 9.5%. It becomes a problem at the shortest focal length where it amounts to as much as 19.5% and prevents the lens from reaching such high MTFs as those of the Sigma 18-250 mm OS for example.
