Sony FE 40 mm f/2.5 G
4. Image resolution
Let's see how the Sony FE 40 mm f/2.5 G compares – its results in the frame centre and on edges of the APS-C and full frame are presented below.
When it comes to the frame centre, the tested lens deserves to be praised. Already at the maximum relative aperture you deal with a high result, reaching almost 65 lpmm and on stopping down you can even exceed 75 lpmm. This performance is not as good as that of the Batis 2/40 and the Sigma C 2/35 (MTFs of both of them were a tad higher than 77 lpmm) but the Sony is a bit slower aperture-wise so its task was more difficult. Still it managed to perform very well, it's enough you compare it to other 2.8/35 class lenses. For example the Zeiss Sonnar 2.8/35 barely exceeded 62 lpmm and the Samyang 2.8/35 could get only as high as 63 lpmm.
Also the situation on the edge of the APS-C sensor should be assessed very positively. At the maximum relative aperture the lens is able to exceed 50 lpmm so it produces completely useful images. Maximum MTFs are reached in an aperture range from f/4.0 to f/5.6 and there you see very good values, of about 60 lpmm.
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When the constructors have to take into account the size of the lens, the edge of full frame is often troublesome. Also in this case you can notice some compromises connected to preserving right physical dimensions. By f/2.5 and f/2.8 the lens lands a bit below the decency level; fortunately on stopping down to near f/3.5 the problem disappears and from f/5.0 to f/9.0 MTF50 function values are on a really good level.
To sum up the Sony FE 40 mm f/2.5 G is a lens completely able to provide images that are sharp almost across the frame. There is a small compromise to be observed on the edge of full frame and at the maximum relative aperture but it's a price worth paying for smaller physical dimensions.
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, 40 mm, f/2.5 |
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| A7R III, JPEG, 40 mm, f/4.0 |
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