Sigma C 17-70 mm f/2.8-4.0 DC Macro OS HSM
6. Distortion
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The immediate predecessor of the tested lens at the wide angle had a noticeable barrel distortion which value amounted to -3.28%. That aberration decreased quickly as the focal length increased, changed the sign and, in the 50-70 mm range reached the level of +1.1%. The new lens compares unfavorably with that performance. At 17 mm we get “barrel” of -4.13% so noticeably higher. At 24 mm you still see barrel deformations but smaller this time, reaching -0.92%. At 35 mm there is already pincushion distortion of 0.52% which increases to 0.88% at 50 mm. After passing to 70 mm the distortion still gets slightly higher, up to a value of 0.99%.
Introducing a new optical construction allowed to decrease the distortion level in the 50-70 mm range (still that effect is so slight that almost imperceptible) but it increased in the place where it is the most bothersome so at 17 mm. Out of the frying pan into the fire…
| Canon 50D, 17 mm | |||
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| Canon 50D, 24 mm | |||
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| Canon 50D, 35 mm | |||
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| Canon 50D, 50 mm | |||
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| Canon 50D, 70 mm | |||
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