Fujinon XF 18-135mm f/3.5-5.6 R LM OIS WR - Review / Test Report - Analysis
Lens Reviews - Fujifilm X

Distortion

Most users will probably take advantage of Fujifilm's image correction system. If so, you will observe a marginal amount of barrel distortion at 18mm. Beyond there isn't really anything to report. Thus it's a pretty much worry-free system.

When looking at the native distortion characteristic, things are very different though. There is a massive barrel distortion (5.1%) at 18mm. At 35mm, you can spot marginal pincushion distortions which increase slightly the more you zoom out to 135mm. However, the pincushion distortions remain very moderate even at the extreme end.

Vignetting

Vignetting is another aspect which is usually auto-corrected. You may observe traces of vignetting at fully open aperture but generally this is nothing to worry about.

Please note that vignetting compensation is also a lossy procedure because it increases the corner (sensor-)noise.

In RAW mode - thus with disabled distortion and vignetting compensation - it is a different story again. At max. aperture there's a strong light falloff especially at 18mm with a peak beyond 2EV (f-stops). Unless you are after the effect you should stop down to f/5.6, better f/8, although the light falloff will never disappear completely at this setting. The issue is very well controlled in the middle range. It increases again at 135mm @ f/5.6 but the amount remains within sane limits.

MTF (resolution)

The Fujinon produced acceptable resolution figures in the MTF lab. The lower portion of the zoom range is clearly better than the long end (as usual for such lenses). At 18mm the center quality is actually very good and the outer image region is actually pretty decent as well. There is a bit of field curvature (non-flat focus field) at this setting though. The center quality remains intact when zooming to 35mm but the borders/corners suffer at large aperture settings. Still - the image quality is very decent around f/8. A slight downward trend continues at 70mm. The weakest setting is reached at 135mm. The center quality is still pretty good but the borders/corners are soft at f/5.6 and just Okay at f/8-f/11.

We tested two samples. The first one had a rather terrible centering quality. The 2nd sample was clearly better but still not perfect. Please allow us to comment that Fujifilm should work on its quality control ...

Below is a simplified summary of the formal findings. The chart shows line widths per picture height (LW/PH) which can be taken as a measure for sharpness. If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations

Chromatic Aberrations (CAs)

Lateral CA (color shadows at the image borders) are well controlled for a standard zoom lens. You may spot traces at 18mm and, more so, at 135mm. However, an average CA pixel width around 1px at the borders is usually not disturbing. The CAs increase in the extreme corners though.