Sigma A 50 mm f/1.4 DG DN review - Image resolution

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Sigma A 50 mm f/1.4 DG DN

3 April 2023

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. The best lenses are able to exceed 80 lpmm and, currently, our list of these record-holders features the Sigma C 65 mm f/2 DG DN (82.7 lpmm), the Sony FE 20 mm f/1.8G (83.7 lpmm), and the Sony FE 50 mm f/1.4 GM (90.9 lpmm).

Let's check how the Sigma A 50 mm f/1.4 DG DN compares – its results in the frame centre and on edges of the APS-C and full frame are presented by a graph below.

Sigma A 50 mm f/1.4 DG DN - Image resolution

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The results by f/2.8 and f/4.0 apertures, amounting to about 80 lpmm, stick out at once. In the first case you deal with a value of 80.8 ± 0.7 lpmm, within the margin of error the same as 81.0 lpmm reached by the Voigtlander Apo Lanthar 2/50, a lens that not so long ago was on our list of record-holders. It's obvious the new Sigma on stopping down is able to reach sensational results, worthy of the best fixed-focal lenses.

Also the situation near the maximum relative aperture is beyond reproach. By f/1.4 the result gets to almost 47 lpmm so is easily above the decency level. Additionally, by f/2.0 image quality improves distinctly, with MTFs exceeding 65 lpmm. The performance on the edge of the APS-C sensor also can be described in superlatives only. Already at the maximum relative aperture you see a result of over 44 lpmm so completely useful. On stopping down the aperture the lens is able to reach near 75 lpmm, also an excellent level.

There is one weak point – a combination of the maximum relative aperture and the edge of full frame where the lens gets to just 38.3 lpmm, a tad lower than the decency level. Still, already on stopping down the aperture to f/1.6 the decency level is reached and by f/2.0 you see a quite sensible result, exceeding 50 lpmm. Near f/4.0 you already get a very good performance, with results close to 67 lpmm.

Practically at every combination of position in a frame and aperture value the Sigma A 50 mm f/1.4 DG DN is noticeably weaker than the new record-holder, the Sony FE 50 mm f/1.4 GM. Still, three things should be mentioned here. Firstly, the Sigma remains a very well-put-together lens, very sharp, performing as it befits an excellent prime. Secondly, it is two times cheaper than the Sony, a huge difference. Thirdly, its resolution outclasses the majority of other 50 mm lenses we've had an opportunity to test.

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

A7R III, JPEG, 50 mm, f/1.4