Sony FE 28-70 mm f/2 GM review

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Sony FE 28-70 mm f/2 GM

18 December 2024

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 about 80 lpmm. Record-breaking lenses are able to exceed 85 lpmm and so far, our list of these record-breakers features the following devices: the Sony FE 85 mm f/1.4 GM II (85.8 lpmm), the Meike 85 mm f/1.4 FF STM (90.2 lpmm), and the Sony FE 50 mm f/1.4 GM (90.9 lpmm).

Let's check how the Sony FE 28-70 mm f/2 GM compares – its results in the frame centre at 28, 50, and 70 mm presents a graph below.

Sony FE 28-70 mm f/2 GM - Image resolution

I don't have any doubts that we deal here with an outstanding performance. To be honest even if such graphs were put into tests of any of 2/28, 2/50, and 2/70 primes I would still call them outstanding. Mind you, here we deal with a zoom lens, much more difficult to construct.

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In order not to sound groundless you can compare here other f/2.0 standards so praised by us, namely the Voigtlander Apo-Lanthar 2/50, a lens that was featured on our lists of record-breakers for a very long time, and the well-put-together Sigma C 50 mm f/2 DG DN.

As you can notice, the Sigma is the weakest here and the Sony and the Voigtlander, are, within the margin of error, equally good, even though, officially, the Sony has higher results and by f/2.8 reaches a value of 82.9 lpmm.

Does the edge of the frame have any weak points? Let's check the situation on the edge of the smaller APS-C sensor.

Once again the 50 mm focal length fares the best, shaming even the sharpest primes. Both ends of the focal range are a bit weaker but still they land at least on a good level because on stopping down the aperture you are able to reach near 60 lpmm and at the maximum relative aperture you get more than a dozen lpmm above the decency level. In other words there are no reasons to complain.

Can you find such reasons on the edge of full frame? Let's glance at a graph below and check.

Here the advantage of the 50 mm focal length is even more distinct and its performance at this point still remains worth an excellent prime lens. In case of 28 and 70 mm focal length the maximum values keep a good level of 50 lpmm. At the same time you don't see any slip-ups, because even at the maximum relative aperture the MTFs get near 46-48 lpm, and it means at least decent quality of images.

The summary of this chapter can only be enthusiastic. The Sony FE 28-70 mm f/2 GM, a zoom lens difficult to construct, offers you a performance worth the best system primes. It really would be foolish to expect more.

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

A7R IIIa, JPEG, 50 mm, f/2.8