Lens review

Viltrox AF 13 mm f/1.4 XF

3 November 2023
Maciej Lata³³o

4. Image resolution

The resolution test of the Viltrox AF 13 mm f/1.4 XF was based on RAW files from the Fujifilm X-T2. We developped the files using the dcraw program (with the 3-pass X-trans algorithm filter) and analyzed them with the help of Imatest package.

Let's remind here that the best fixed focal length Fujifilm X lenses, tested that way, are able to reach as high as 80 lpmm, with record results hovering around 85 lpmm and higher, and the decency level is set near 44-45 lpmm. The resolution records for this sensor belongs to the Fujinon XF 56 mm f/1.2 R WR (92.8 ±1.1 lpmm) and the Fujinon XF 18 mm f/1.4 R WR (93.5 ±0.9 lpmm).

Now let's see how the Viltrox AF 13 mm f/1.4 XF compares in the frame centre and on its edge – the appropriate graph you can see below.

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Viltrox AF 13 mm f/1.4 XF - Image resolution

In the frame centre you get everything you would expect from a good quality fixed-focal lens. At the maximum relative aperture the result is very nice, reaching over 70 lpmm, and on stopping down the lens by 2 EV the resolution approaches an excellent level of 80 lpmm.

Still it was very interesting how such a wide angle of view performs when joined with such a good aperture fastness. Here we've got no good news because the difference between the centre and the edge of the frame is really huge. The problems are so pronounced that by f/1.4 the lens's resolution descends a bit below the decency level. Fortunately the resolution increases on just slight stopping down to f/1.6-1.8 and it becomes quite decent but this increase is relatively slow so only by f/4.0-8.0 you can speak about a very good image quality.

Our summary will be positive, though. With such extreme parameters it is very difficult to guarantee high image quality across the frame up from the maximum relative aperture. The fact that f/1.6-1.8 apertures allow you to reach images which are beyond reproach even at the very edge of the frame is still impressive. Is it possible to construct a better instrument with such parameters? Perhaps, but so far only Viltrox has been brave enough to try.

At the end of this part of our test, traditionally, we present crops taken from photos of our resolution testing chart which were saved in the JPEG format along with RAW files, used for the analysis above.

Fujifilm X-T2, JPEG, f/1.4
Viltrox AF 13 mm f/1.4 XF - Image resolution
Fujifilm X-T2, JPEG, f/2.8
Viltrox AF 13 mm f/1.4 XF - Image resolution