Sigma A 24-70 mm f/2.8 DG OS HSM review - Distortion

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Sigma A 24-70 mm f/2.8 DG OS HSM

28 July 2017

Arkadiusz Olech

6. Distortion

As long as you work on the smaller APS-C/DX sensor the distortion shouldn't be especially bothersome. With the lens attached to the Canon 50D we got for 24, 28, 35, 50 and 70 mm focal lengths respectively: –1.89%, −1.15%, −0.34%, +0.29% i +0.59%. Slight „barrel” distortion can be noticeable only in the 24-28 mm range but even there it cannot be called especially annoying.

The situation changes a lot when you pass to full frame and you feel that rather keenly at 24 mm where you see distinct moustache distortion. After averaging out the results from the whole frame you get −3.31%. If you limit yourself only to the area inside the 1:1 markers then the barrel distortion increases to −4.19%. What's interesting, at 28 mm the result is far more acceptable, amounting to −1.83%, but it has nothing to do with reality because moustache distortion is still present there. What's even more interesting, it can be noticed even at the 35 mm focal length where the official result is −0.30%, lower than that we got on the 50D camera just because those moustache-style deformations.

The results of the Canon EF 24–70 mm f/2.8L II USM and the Tamron SP 24–70 mm f/2.8 Di VC USD at 24 mm were weaker and both those lenses also were helped by moustache distortion but it disappeared already at 28-35 mm. The Nikkor AF-S 24-70 mm f/2.8E ED VR had a result of −4.23% for a change but in its case it was difficult to notice any moustache-style deformations even at 24 mm.

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Returning to the performance of the Sigma A 24-70 mm f/2.8 – its distortion problems end at 50 and 70 mm where you deal with slight pincushion variation of +0.88% and +1.61% respectively. These are lower than the results of the stabilized Nikkor and, at the same time, higher than the results of the Canon, the Tokina and the Tamron.