Lens review

Sigma A 70 mm f/2.8 DG Macro

30 June 2018
Arkadiusz Olech

4. Image resolution

The resolution test (resolution meaning MTF50 function) of the Sigma A 70 mm f/2.8 DG Macro was based on RAW files from the Canon EOS 5D Mark III. In the case of that reflex camera the decency level is situated near 30-32 lpmm and high quality, top-of-the-range fixed focal lenses can reach a maximum level of 45-49 lpmm . Not so long ago the resolution record for that sensor belonged to the Zeiss Otus 1.4/28 (49.2 lpmm) but it’s been slightly beaten by the Sigma A 85 mm f/1.4 DG HSM, an then by the Sigma A 135 mm f/1.8 DG HSM and currently it amounts to 51.6 lpmm .

Let’s check how the tested Sigma A 70 mm f/2.8 DG Macro compares – a graph below presents its results in the frame centre, on the edge of the APS-C/DX sensor, and on the edge of full frame.

Sigma A 70 mm f/2.8 DG Macro - Image resolution

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The frame centre is sensationally good. Already at the maximum relative aperture you get results higher than 46 lpmm – it’s a level older constructions could only dream of. By f/4.0 you see a resolution level of 48.6 lpmm , perhaps not record-breaking but very close to that. It is within margin of error exactly the same value as the result of the Otus 1.4/28, mentioned in the introduction to this chapter, a lens almost ten times more expensive than the Sigma.

The edge of the APS-C/DX sensor is equally sensational. You get to 40 lpmm already at the maximum relative aperture and on stopping down the aperture to f/4.0 the lens can reach results near 45 lpmm.

The MTFs for the edges of full frame sensor are a bit different. The values remain excellent because already at the maximum relative aperture the lens exceeds a very high level of 39 lpmm but this time the peak of the performance is not observed by f/4.0 but by f/5.6, where the MTFs are able to exceed 42 lpmm.

When it comes to resolution the tested Sigma has no weaknesses – its fares exceedingly well and its performance is worthy of other Art line lenses. At the end of this part of the test traditionally we present crops taken from photos of our resolution testing chart saved as JPEG files.

Canon 5D MkIII, JPEG, 70 mm, f/2.8
Sigma A 70 mm f/2.8 DG Macro - Image resolution
Canon 5D MkIII, JPEG, 70 mm, f/4.0
Sigma A 70 mm f/2.8 DG Macro - Image resolution