Lens review

Sigma C 90 mm f/2.8 DG DN

8 November 2021
Maciej Latałło

4. Image resolution

Our resolution test (resolution meaning the MTF50 function values) of Sony FE lenses is based on RAW files from the 42.4 Mpix sensor of the Sony A7R II or the Sony A7R III camera. In the case of this kind of detector the decency level we set about 39-41 lpmm and the best fixed focal lenses have been able to reach a level of 75-80 lpmm. Record-breaking lenses exceed slightly 80 lpmm and, so far, our list of record-breakers features the Voigtlander Apo Lanthar 50 mm f/2 E (81.0 lpmm) and the Sigma C 65 mm f/2 DG DN (82.7 lpmm).

Let's check how the Sigma C 90 mm f/2.8 DG DN compares – below you can find a graph with its results in the frame centre and on edges of the APS-C and full frame sensors.

Sigma C 90 mm f/2.8 DG DN - Image resolution

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A very even performance is something that sticks out at once – there are no big differences between the frame centre and its edge. The second important thing is how the lens fares at the maximum relative aperture. In the frame centre it is able to exceed 63 lpmm, on the edge of the APS-C it lands above 60 lpmm and on the edge of full frame it gets over 56 lpmm. All these results guarantee you good image quality.

In the frame centre, on stopping down to f/4.0, the lens is able to reach 75.5 lpmm. It's hardly a record-breaking level but nobody would expect any records from an f/2.8 lens. More important is the comparison between the Sigma and its direct rivals and that is very favourable indeed. For example the Sony FE 2.8/90 Macro barely exceeded 70 lpmm, the Viltrox PFU RBMH 85 mm f/1.8 STM was able to reach just about 65 lpmm and the Samyang AF 75 mm f/1.8 FE – 74 lpmm. As you see, the Sigma is the sharpest in this group and also its perfomance is very even. Taking into account its aperture and physical dimensions the result in this category we find simply sensational – a round of applause!

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, 90 mm, f/2.8
Sigma C 90 mm f/2.8 DG DN - Image resolution
A7R III, JPEG, 90 mm, f/4.0
Sigma C 90 mm f/2.8 DG DN - Image resolution