Zeiss Touit 12mm f/2.8 (Sony E) - Review / Test Report - Analysis
Lens Reviews -
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The Zeiss 12mm f/2.8 produces a barrel distortion of 2% which is actually quite good for a prime lens in this class.
Light falloff is a weak spot for many native ultra-wide lenses on mirrorless camera. This is also true for the Zeiss lens. At max. aperture there is an extreme vignetting of 2EV (f-stops) and when stopped down to medium apertures you'll still have to live with about 1EV (f-stop).
Ultra wide angle lenses are already difficult to design but the optical problems are 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 stay just short of the 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 - this is comparatively "early".
The centering quality of tested sample was good. The field curvature is quite low.
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 1px lateral CAs (color shadows at hard contrast transitions) are 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 decent results. The center quality is great and the border and corner quality are good to very good at mainstream settings. The low lateral CAs contribute to the high sharpness perception. The distortions are 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 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. 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.
A key question is, of course, how the Zeiss lens performs compared to its nearest rival - the Sony 10-18mm f/4 OSS. We haven't tested the Sony lens at 12mm but the overall results are probably similar. It is likely that the Zeiss lens has sharper corners at f/4. However, even assuming a similar performance of the Sony lens, we'd still prefer the Zeiss lens simply because of better QC and more robust design.
PS: In the October time-frame we'll do a reference test on the A6000 in order to verify the corner behavior of the new sensor. The NEX7 sensor is a fairly "difficult" being in this respect in our opinion.