Lens review

Sony FE 85 mm f/1.4 GM

14 September 2016
Arkadiusz Olech

4. Image resolution

The resolution test (resolution meaning the MTF50 function values) of the Sony FE 85 mm f/1.4 GM was based on RAW files from the Sony A7R II. In the case of that mirrorless camera the decency level is situated near 38-40 lpmm and the best fixed focal length lenses can reach results as high as 64-67 lpmm. Mind you, so far we have based those values on a small sample of primes tested by us so in further tests they might be verified a bit.

Let’s check how the tested lens compares; its results in the frame centre, on the edge of the APS-C sensor and on the edge of the full frame presents a graph below.

Sony FE 85 mm f/1.4 GM - Image resolution

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When it comes to the frame centre the performance of the lens is simply splendid. Already at the maximum relative aperture the MTFs reach almost 41 lpmm so are safely above the decency level. The resolution increases very quickly and by f/2.8 the lens gets to 69.1 lpmm, the highest result recorded by us in our tests while using the Sony A7R II. At the same time such a value is by several lpmm higher than the results of the Sonnars FE 2.8/35 and 1.8/55, considered by us as exceedingly sharp.

The resolution on the edge of the APS-C sensor also should be called very good. Even at the maximum relative aperture the MTFs exceed slightly 38 lpmm so the image is useful. On stopping down the aperture the image quality increases sharply and by f/2.8 you already deal with a very high result of over 58 lpmm.

When you glance at the edge of full frame your feelings might be mixed. On the one hand, compared to the older 85 mm class constructions, it looks well. On the other hand such lenses like the Zeiss Otus or the Zeiss Milvus could have noticeably smaller differences between their performance in the frame centre and on the edge of full frame. Once again the small distance between the rear element of the tested lens and the huge sensor of the camera is perhaps the cause.

To sum up we don’t have any doubts that the performance of the Sony FE 85 mm f/1.4 GM fits the level marked by the Zeiss Milvus and Otus more than the level of older but also very well-done constructions. There is plenty of proof: the full usefulness by f/1.4 in the frame centre and on the edge of the APS-C sensor along with the resolution records you get in the f/2.8-4.0 range.

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

A7R II, JPEG, f/1.4
Sony FE 85 mm f/1.4 GM - Image resolution
A7R II, JPEG, f/2.8
Sony FE 85 mm f/1.4 GM - Image resolution