Zeiss Touit 12mm f/2.8 (Fujifilm) - Review / Test Report - Analysis
Lens Reviews -
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Just like its 32mm cousin, the Zeiss 12mm f/2.8 isn't totally corrected in terms of distortions. In untouched RAW files, it shows a barrel distortion of 2%. To be fair - this is certainly very moderate for such an ultra-wide angle lens. With activated auto-correction the issue decreases to a very slight 0.8% barrel distortion. This value may vary across different RAW converters since the lens profiles can differ.
If you move your mouse cursor over the image you can switch to the corresponding "raw" results.
The auto-correction is also active for vignetting. Corrected JPEG images show a light falloff of 0.9EV (f-stops) at f/2.8. While this is visible in certain scenes, it is comparatively moderate for a lens in this class. As usual the vignetting decreases when stopping down and it's not really relevant anymore beyond f/4 (below 0.5EV).
Uncorrected RAWs show a very different story with a very high falloff of more than 1.8EV at max aperture and still 1.2EV at f/4. The issue is never really gone with just under 1EV at the best setting (f/8).
Ultra wide angle lenses are already difficult to design. The optical problems are then even magnified on mirrorless cameras with their short sensor to rear element distance in conjunction with recessed photodiodes on the sensor. Now keeping this in mind, the Zeiss Touit 12mm f/2.8 does a very good job in terms of resolution. The center quality is excellent straight from f/2.8 and it already peaks at f/4. The border and corner quality hovers a bit around the good to very good mark with the best results at f/5.6. It is worth to note that the good corner quality at max aperture is quite surprising. On the other hand, f/11 should be avoided due to the more pronounced diffraction effects.
The centering quality of tested sample was fairly good. The field curvature is quite low.
Please note that the results were obtained from uncorrected RAWs. The quality of the (distortion-)corrected images depends on the specific converter so we decided to avoid this discussion here.
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
Chromatic Aberrations (CAs)
At around 0.4px lateral CAs (color shadows at hard contrast transitions) are very low and usually nothing to worry about.
VerdictUltra-wide angle lenses are never really perfect. However, within its scope the Zeiss Touit 12mm f/2.8 delivers pretty impressive results. The center quality is great and the border and corner quality are good to very good at mainstream settings. The very low lateral CAs contribute to the high sharpness perception. Distortions and vignetting are usually auto-corrected either by the camera or your favorite RAW converter so you don't have to worry about these aspects from a normal user perspective. However, when looking at the naked raw files, you can spot a few issues. The raw distortions are actually still quite fine at 2% - this is a normal value for such a prime lens and lower than on most conventional zoom lenses for sure. However, the raw vignetting is very high especially at max. aperture.
Overall we liked the build quality - and looks - of the Zeiss lens. The incorporated materials are obviously of high quality. However, the implementation of the aperture ring may not be perfect - while it provides distinctive "clicks" you tend to change the setting by (un-)mounting because it turns too easily. Just like on the Zeiss Touit 32mm f/1.8 we weren't totally convinced by the AF but it does an Okay job in terms of AF speed and the generated noise level is quite low. As mentioned we still used an old X-E1 for the test so the AF performance is probably a much lesser issue on the X-E2 and X-T1 anyway.
A key question is, of course, how the Zeiss lens performs compared to its nearest rival - the Fujinon XF 14mm f/2.8 R. The Fuji lens is slightly sharper in the image corners at medium apertures but then it's also not quite as wide. These two extra millimeters can make quite a difference. To phrase it differently: the diagonal view angle the Zeiss lens reaches 99 degrees vs 89 degrees for the Fuji lens. Thus if you are after an even more dramatic perspective in your images, the Zeiss may be the more interesting choice.