Sony FE 20 mm f/1.8 G review - Image resolution

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Sony FE 20 mm f/1.8 G

16 May 2022

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 length lenses have been able to reach 75-80 lpmm. So far, two lenses have fared the best: we mean here the Voigtlander Apo Lanthar 50 mm f/2 E (81.0 lpmm), and the Sigma C 65 mm f/2 GD DN (82.7 lpmm).

Let's check how the Sony FE 20 mm f/1.8G fares – its results in the frame centre and on edges of the APS-C sensor and full frame presents a graph below.

Sony FE 20 mm f/1.8 G - Image resolution

The performance of the tested lens in the frame centre is simply incredible. It is quite an achievement, to produce a fast, sharp ultra wide angle lens but to produce a lens which resolution, up from the maximum relative aperture, lands close to record values is a real masterpiece.

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That's why the resolution showed by the Sony FE 20 mm f/1.8G is so incredible – already by f/1.8 the lens is able to exceed slightly 81 lpmm, by f/2.0 it reaches 82.1 lpmm and by f/2.8 we get a new record, amounting to 83.7 lpmm. Hats off!

Of course preserving small physical dimensions of the lens was one of priorities here – that's why, after a brilliant performance in the frame centre, we didn't expect the edges to fare equally good. It would be physically impossible. Indeed the results are weaker but only because we compare it to the fantastic resolution levels in the frame centre. In the absolute reference scale, taking the offered parameters into account, they still should be called very good.

On the edge of the APS-C sensor even at the maximum relative aperture you get sensible image quality without any problems and on stopping down the aperture that quality improves very quickly, reaching its maximum near f/4.0 with very good values of over 63 lpmm.

When it comes to edges of full frame, very demanding with such lens parameters, you can be a tad unsatisfied only near the maximum relative aperture, where MTFs are 35 lpmm. Images become fully useful up from f/2.2 and by f/4.0 their resolution brushes against a level of 60 lpmm.

The summary can only be very positive – we are pleasantly surprised that such a small, shapely ultra wide-angle lens can perform so well.

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, 20 mm, f/1.8