Viltrox AF 15 mm f/1.7 Air
4. Image resolution
Let’s remind here that the best fixed focal length Fujifilm X lenses, tested that way, can reach as high as about 90 lpmm and the decency level is situated near 44-45 lpmm. So far the best resolution we measured while testing the Fujinon XF 18 mm f/1.4 R WR (93.5 ±0.9 lpmm), the Viltrox AF 27 mm f/1.2 (97.5 ±1.5 lpmm) and the Viltrox 75 mm f/1.2 (99.8 ±1.2 lpmm).
Let's check how the Viltrox AF 15 mm f/1.7 Air compares here – its results in the frame centre and on the edge of the frame presents a graph below.
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I admit that the performance of the small Viltrox in the frame centre shocked me in a very positive way. You see not only a sensational result, reaching almost 76 lpmm at the maximum relative aperture, but on stopping down it gets to 92.7 lpmm so, within the margin of error, it brushes against the podium reserved for our resolution records. I didn't expect such a performance from a small lens priced at $240. The next Viltrox launch and the next proof that they know their business and can design really sharp lenses.
The results presented on the edge of the frame are noticeably lower and might seem to be weak; in fact they are anything but. It's just an effect created by a comparison to the outstanding results in the frame centre. After all even at the maximum relative aperture the edge gives you a result of almost 52 lpmm so definitely higher than the decency level. At the beginning the resolution increases slowly and it is partially connected to the local chromatic aberration maximum point, appearing by f/2.8 (more about it in the next chapter) but then MTFs are able to exceed a very good level of 60 lpmm without any problems.
With such an angle of view and aperture fastness combined with a very accessible price I expect a lot of compromises, especially on the edge of the frame. Meanwhile the tested Viltrox not only doesn't show any substantial compromises but it was able to hover around resolution records in the frame centre – a round of applause!
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.
| Fujifilm X-T2, JPEG, f/1.7 |
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| Fujifilm X-T2, JPEG, f/2.8 |
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