Zeiss went to substantial effort with the Batis 18mm f/2.8 Distagon:
The super wide-angle camera lens has 11 lens elements in ten groups and draws on the ZEISS Distagon optical design.
Four of the lens elements are aspheric on both sides and seven are made from special types of glass.
The Floating Elements design permits constantly high image performance in the focal plane – from the minimum object distance to infinity.
The use of four double-sided aspherics is highly unusual, and 7 of the 11 are made from glass of a special type. Can you spot the lens element that is not special in some way? There are none. This sophisticated design is a trend that I applaud.
The MTF charts tell a strong story, but field shooting shows an 18mm performer that has no peer including shots at MOD (minimum object distance). With dust and moisture resistance plus autofocus, the Sony mirrorless shooter looking for an extreme wide angle need look no further. At about $1499, The Zeiss Batis 18mm f/2.8 Distagon offers serious value for the performance: consider that the Leica 18mm f/3.8 Super-Elmar-M ASPH is about $2860 and while a very satisfying performer, it shows its limits on only a 24MP megapixel sensor in the outer zones.
Now I just want to see a Canon-style Zeiss Loxia or Batis 11-16mm f/4 zoom.