7Artisans 12mm f/2.8 (Sony E-mount) - Review / Test Report - Analysis
Lens Reviews - Sony Alpha/NEX (APS-C)

Distortion

One of the most surprising aspects of this lens is the distortion characteristic. Mirrorless lenses tend to show heavy barrel distortion and rely on auto-correction. Instead, the 7Artisans 12mm f/2.8 shows a negligible amount of pincushion distortion (0.6%).

Vignetting

The light falloff isn't quite as impressive though. The vignetting exceeds our usual scale for APS-C format lenses at f/2.8. Stopping down improves this gradually but the falloff is still very visible at f/8 (~1.4EV). To be fair - the Zeiss Touit 12mm f/2.8 and Sony 10-18mm f/4 didn't excel here either.

MTF (resolution)

The resolution characteristic is quite good albeit of course, not without flaws. The center quality is excellent straight at f/2.8. The borders/corner are soft at this setting though. Stopping down boosts the quality and you can expect a good outer field at f/5.6. Interestingly the corners are better than the borders throughout most of the range - this is quite rare. The sweet spot is at f/8 with good to very good results at the borders/corners. Diffraction has a higher impact beyond f/11. f/11 remains quite usable though.

Field curvature is present but not extreme. There are some variations in terms of centering (optical alignment) but that's to be expected at this price point.

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)

Lateral CAs are on a low level with an average CA pixel width of around 0.6px mark at the image borders.

Flare

Many ultra-wide lenses struggle when it comes to flare in backlit situations. However, the 7Artisans 12mm f/2.8 is - surprisingly - quite decent in this respect. Below is an extreme example taken at f/8. You can spot a few ghostings in there but it's far from being bad.