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Lens review

Fujifilm Fujinon XF 16-50 mm f/2.8-4.8 R LM WR

3 February 2025
Maciej Lata³³o

6. Distortion and field of view

Distortion

The Fujinon XF 16-50 mm f/2.8-4.8 R LM WR attached to the Fulifilm body forces an automatic distortion correction – it means JPEG files are already corrected for this kind of aberration. It would be difficult to expect any strong deformations.

At 16 mm it is the easiest to notice as you deal with a 'barrel' of -1.33%. It's significant that the software of the camera wasn't able to correct distortion completely. Interestingly enough (and why it is so interesting we are going to explain when we pass to the analysis of RAW files) at the 23 mm focal length you already deal with 'pincushion' of +0.70% and at 35 mm it decreases to +0.51%; what's even more interesting, at 50 mm it changes the sign once again, amounting to -0.71%.

Fujinon X-T2, JPEG, 16 mm
Fujifilm Fujinon XF 16-50 mm f/2.8-4.8 R LM WR - Distortion and field of view
Fujinon X-T2, JPEG, 23 mm
Fujifilm Fujinon XF 16-50 mm f/2.8-4.8 R LM WR - Distortion and field of view
Fujinon X-T2, JPEG, 35 mm
Fujifilm Fujinon XF 16-50 mm f/2.8-4.8 R LM WR - Distortion and field of view
Fujinon X-T2, JPEG, 50 mm
Fujifilm Fujinon XF 16-50 mm f/2.8-4.8 R LM WR - Distortion and field of view


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An analysis of RAW files developed by an independent software such as dcraw shows the real situation concerning deformations, generated by the optics of the tested Fujinon.

The problems are really huge here because at the 16 mm focal length you deal with a very high level, that of -7.06%. With the lengthening of the focal length distortion decreases and at 23 mm it reaches -1.27%. You still deal with barrel distortion but the same focal length showed a measureable 'pincushion' in JPEG files. It's clear that even the camera's software goes haywire here and overcorrects distortion distinctly.

At the 35 mm focal length you deal with distinct 'pincushion' of +1.82% that decreases to +1.65% on passing to the maximum focal length. In its case the camrea's software once again went over the top overcorrecting distortion and steering it towards negative values for JPEG files.

Fujinon X-T2, RAW, 16 mm
Fujifilm Fujinon XF 16-50 mm f/2.8-4.8 R LM WR - Distortion and field of view
Fujinon X-T2, RAW, 23 mm
Fujifilm Fujinon XF 16-50 mm f/2.8-4.8 R LM WR - Distortion and field of view
Fujinon X-T2, RAW, 35 mm
Fujifilm Fujinon XF 16-50 mm f/2.8-4.8 R LM WR - Distortion and field of view
Fujinon X-T2, RAW, 50 mm
Fujifilm Fujinon XF 16-50 mm f/2.8-4.8 R LM WR - Distortion and field of view

It's a fact: universal zoom lenses with such features as low weight and small physical dimensions being close to the top of the priority list of their constructors are often burdened with different compromises. Neglecting distortion is one of more obvious and not especially damaging option. Fujifilm optics specialist have chosen this option and you can hardly blame them. Still the low damaging factor is conditional – it can't hurt providing that the producers left enough spare field of view. Is it the case? We are going to find out in a while.

Field of view

A rectilinear lens with focal lengths ranging from 16 to 50 mm on an APS-C sensor so with 1.5x ratio should provide you an angles of view changing from 83.1 to 31.7 deg. The producers in their official specifications state almost identical values of 83.2-31.7 deg.

Of course we decided to check how big this field really is. In order to do so we took photos of starry sky and saved them as both corrected JPEG files and uncorrected RAW files.Then we transformed the pixel layout (X,Y) from the photo into the equatorial coordinate system (right ascension and declination), which locates a star on a celestial sphere. That way we could determine the field of view of the lens with utter precision and in the right way, so for rays of light coming from infinity.

In case of the shortest focal length and JPEG file format we used 82 stars spread evenly across the frame and the average mesh-fitting error amounted to 27 seconds of arc. We got a result of 84.17 deg with an error that doesn't exceed 0.05 of a degree.

We admit the producers behave in an exemplary manner. Even in the JPEG format the field is about one degree higher than the official declarations so we get some area to spare allowing you to correct slight distortion still visible after passing from RAW files.

At the 50 mm focal length and JPEG format we used 79 for the transformation and the average mesh-fitting error amounted to just 8 seconds of arc. We got a result of 31.74 deg with an error of 0.02 of a degree.

It's clear that the producers approached the distortion problem in a very honest way and the field sizes concern already corrected files. It means that in case of RAW files you can enjoy a field much wider than stated in technical specifications.

For RAW files in case of the 16 mm focal length our transformation was based on the location of 125 stars spread evenly across the frame and the average mesh-fitting error amounted to 1 minute and 37 seconds of arc. We got a result of 88.86 deg with an error of about 0.08 of a degree. Compared to official declarations it is over 5 degrees more – a significant amount of spare field. Here you get a field of view of a rectilinear lens of a focal length amounting to 14.5 mm or so.

At the maximum focal length we used 81 stars for our transformations and the average mesh-fitting error amounted to just 6 seconds of arc. We got a result of 31.86 deg with an error that doesn't exceed 0.05 of a degree. Here the amount of spare field is much smaller but, at the same time, in case of the 50 mm focal length we don't need it as much as at the shortest focal length so it's still ok.