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Lens review

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

28 July 2017
Maciej Latałło

11. Summary

Pros:

  • Solid casing designed for high rigidity,
  • Excellent image quality in the frame centre,
  • Good image quality on the edge of the APS-C,
  • Lack of problems with longitudinal chromatic aberration,
  • Sensible coma correction,
  • Low vignetting on the APS-C/DX,
  • Silent, quick and accurate autofocus,
  • Efficient image stabilization.

Cons:

  • Resolution on the edge of the frame at the 70 mm focal length should have been better,
  • Noticeable problems with spherical aberration,
  • Weak performance against bright light,
  • A bit too high astigmatism level,
  • Significant vignetting on full frame,
  • Noticeable distortion of moustache style on the wider end of the focal lengths range.
So far the Art series Sigma lenses have spoilt us rotten – usually they beat their rivals hands down in practically every category while being significantly cheaper. Still every winning streak comes to an end and the A 24-70 mm f/2.8 DG HSM OS model is such an ending. It should be noticed that the competition is very fierce in this segment so the ranking can be put completely upside down as you pass from one testing category to another.

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The Sigma fares excellently well in the frame centre and on its edge but only at the shorter focal lengths, doing it at the expense of the edges of the frame at 70 mm. It deals well with chromatic aberrations but the spherical variety remains a problem. The coma correction is not bad but when it comes to the astigmatism it is actually the weakest lens in the group. We also weren't impressed by the fact that the moustache distortion appears in such a wide focal lenths range, from 24 to 35 mm; still the overall level of deformations can be lower than in the case of the competitors. In the vignetting category the Sigma doesn't stick out in any way and its performance against bright light is simply weak. All in all it seems the new Sigma lens is a bit optically weaker than the Canon or the Tokina but, contrary to them, it features a vibrations reduction unit; it is also cheaper than the Canon and its autofocus is better than that of the Tokina. As you see you can go on and on in such a way without reaching any conclusion. It proves that in the 24-70 mm f/2.8 class the choice is rich and it's sometimes difficult to find the best lens. Small nuances and the price might be decisive factors and here, in my opinion, the Sigma won't have it easy. A level of $1300 is dangerously close to prices of the Canon and the Nikkor; it is also more than price tags of the optically very good Tokina and the previous version of the stabilized Tamron. The faster the price of the Sigma decreases the bigger are chances that its share of that very prestigious cake will be significant. In this segment there are simply no weak lenses so the standards are set really high.