Lens review

Sigma C 50 mm f/2 DG DN

29 September 2023
Maciej Lata³³o

4. Image resolution

Our resolution tests (resolution meaning the MTF50 function values) of different Sony FE lenses are based on RAW files from the 42.4 Mpix sensor of Sony A7R II or Sony A7R III cameras. In the case of this kind of detector the decency level we set about 39-41 lpmm, the best fixed focal length lenses have been able to reach 75-80 lpmm and record-breakers have exceeded distinctly 80 lpmm, sometimes even getting close to 90 lpmm. So far, our list of such outstanding lenses includes: the Sigma C 65 mm f/2 DG DN (82.7 lpmm), the Sony FE 20 mm f/1.8G (83.7 lpmm) and the Sony FE 50 mm f/1.4 GM (90.9 lpmm).

Let's check how the Sigma C 50 mm f/2 DG DN compares – below you can find its results in the frame centre and on edges of APS-C sensor and full frame.

Sigma C 50 mm f/2 DG DN - Image resolution

The frame centre is simply splendid. Already at the maximum relative aperture the results are good, with the lens reaching over 57 lpmm. That level improves very quickly on stopping down the aperture so by f/2.8 the Sigma gets to almost 73 lpmm and by f/4.0 it is able to achieve an excellent level of almost 78 lpmm.

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Still, the fact that C series lenses are small means there have to be some compromises. They often concern resolution on the edges of the frame. However, in case of the tested model we couldn't find anything at all, quite the opposite. On the edge of the APS-C sensor the performance of the lens is very good, almost as good as the values you see in the frame centre.

The edge of full frame is the weakest – the performance of the lens improves quite slowly on stopping down. Still, even at the maximum relative aperture and near it the results brush against a quite nice level of 50 lpmm; on stopping down the Sigma is able to get to almost 60 lpmm.

At the end of this chapter we would like to compare directly the tested Sigma and the Voigtlander Apo-Lanthar with exactly the same parameters. In order to make it even more interesting, let's add also the performance of the Sony FE 50 mm f/.8, a simple double gauss lens.

Sigma C 50 mm f/2 DG DN - Image resolution

As you can notice, the Sigma and the Voigtlander are able to outclass the older optical system even though they are a bit slower. What's more, the Apo-Lanthar is a lens sharper than the Sigma practically across the whole aperture range. Of course we have to add that this duel is on such a high level that the Sigma shouldn't be criticized at all for the defeat.

At the end of this chapter, traditionally, we present crops taken from photos of our resolution testing chart saved in JPEG format alongside RAW files which we used for the analysis above.

A7R III, JPEG, 50 mm, f/2.0
Sigma C 50 mm f/2 DG DN - Image resolution
A7R III, JPEG, 50 mm, f/4.0
Sigma C 50 mm f/2 DG DN - Image resolution