|
Page 2 of 3
Distortion
As with many other XF lenses, Fujifilm applies software correction to address the native distortion of the lens.
With this correction applied, there is literally no visible distortion in the images. When switched off (some RAW converters can do this, like Capture One for example), the small amount of native pincushion distortion becomes visible.
Vignetting
Just like distortion, vignetting is also automatically corrected. Even after the correction is applied, there is a fairly visible amount of corner darkening left at the largest aperture setting. Stopped down to f/5.6 and beyond, it is no longer noticeable.
The native, uncorrected vignetting is surprisingly high, reaching above 1.8 stops at f/2.8.
Most users will likely rely on the automated vignetting correction and never notice the lens' high native vignetting. However, one should be aware of the drawbacks of software corrected vignetting (like increased corner noise).
MTF (resolution)
The lens delivers impressive resolution in the lab. The image center is excellent straight from the maximum aperture and stays on this high level until diffraction takes its toll at medium and small apertures.
The borders and corners start one mark lower at f/2.8, but stopping down increases the resolution to excellent levels here, too.
The performance peak is reached at f/5.6 with excellent resolution across the frame.
Please note that the MTF results are not directly comparable across the different systems!
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)
The lateral CAs (color shadows at hard contrast transitions) are well controlled with values below half a pixel at large and medium aperture settings, increasing to 0.6 to 0.7 pixels stopped down to f/11 and beyond.
Bokeh
The Fujinon delivers a very smooth and pleasing image blur in the out of focus areas, including the transition zone from in-focus to out-of-focus. Only in front of the focus plane, the bokeh looks a bit nervous.
Background highlights are nicely rendered as evenly filled discs with a tad of outlining.
Bokeh - Cat's Eye
Due to mechanical vignetting, background highlights are rendered as cat's eyes towards the edges of the frame, especially at large apertures. The charts below give an impression of how highlights are deteriorated or slightly cut off at various aperture settings.
In real life images, this vignetting leads to 'swirly' bokeh especially at large apertures, as it can be seen in some of the sample images on the next page.
Bokeh Fringing
Bokeh fringing (non-coinciding focal planes of the various colors) is a common issue with relatively fast glass. It often shows up as halos of different colors - magenta (red + blue) in front of the focus point and green beyond. Unlike lateral CAs, bokeh fringing cannot easily be fixed in post-processing.
The XF 80 is not marketed as an APO lens, but still shows only a very small amount of bokeh fringing wide open. From f/4 onwards, hardly any fringing is noticeable.
|
