Lens review

Sigma A 105 mm f/2.8 DG DN Macro

27 November 2020
Maciej Latałło

4. Image resolution

The resolution test (resoltuion meaning the MTF50 function values) of the Sigma A 105 mm f/2.8 DG DN Macro was based on RAW files from the Sony A7R II camera. In the case of that mirrorless device the decency level we set about 39-41 lpmm and the best fixed focal length lenses have been able to exceed 70 lpmm. So far, two Voigtlander lenses have fared the best: the Apo-Lanthar 65 mm f/2 Aspherical 1:2 Macro (78.5 lpmm) and the Nokton 50 mm f/1.2 (78.6 lpmm). The Zeiss Batis 40 mm f/2 CF (77.1 lpmm) remains very close behind them.

Let's check how the Sigma A 105 mm f/2.8 DG DN Macro compares – its results in the frame centre, on the edge of the APS-C sensor and on the edge of full frame presents a graph below.

Sigma A 105 mm f/2.8 DG DN Macro - Image resolution

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One glance at the results and you know that in this chapter there will be only praise. At the maximum relative aperture the Sigma reaches 78.3 lpmm, brushing against the official record. Still, it's only the beginning of good news - what it failed to achieve by f/2.8 the lens more than made up for by f/4.0 where its resolution is on a completely unique level of 80.4 +\- 1.3 lpmm, defeating noticeably the previous record holders.

The results on the edge of the APS-C sensor are weaker but only because the frame centre fares sensationally well; it would be really difficult to beat that. Overall, MTFs are so good in this place that we've seen many primes that had similar results but in the frame centre. Once again the tested Sigma deserves a round of applause.

The very demanding edge of full frame also doesn't give us any reasons to worry. Already at the maximum relative aperture you get a value of over 50 lpmm so noticeably above the decency level. On stopping down the resuls are near 60 lpmm so could be described as very good. It would be really foolish to expect here anything more.

The more expensive brand name lens, so the Sony FE 90 mm f/2.8 Macro G OSS, loses to the Sigma spectacularly across the whole frame and at all aperture values – you couldn't give the Sigma a better write-up.

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

A7R II, JPEG, 105 mm, f/2.8
Sigma A 105 mm f/2.8 DG DN Macro - Image resolution
A7R II, JPEG, 105 mm, f/4.0
Sigma A 105 mm f/2.8 DG DN Macro - Image resolution