As I’ve said before ultra-wide primes is an area where I hope Zeiss will come out again and shine. Today they just launched a lens in this space, but we’ll have a to wait a bit longer to know how good it really is because MTF isn’t posted yet.
The new Zeiss ZF 3.5/18 Distagon T* is surprisingly compact at 8cm long (on my screen it seems about life-size above, maybe even a bit bigger). For scale, Canon shooters should recall that the F mount is quite a bit smaller than the EOS mount. The filter mount is huge however at 82mm, promising very high cost of filters.
It’s likely that the new lens will beat what’s currently available in this space, because what’s there isn’t that great. See how the Nikon/Canon pretty much give up beyond 2/3s of the frame:
There are better lenses than this today on rangefinder mounts, for example the Zeiss ZM 4/18 Distagon T* for Leica's M-mount (compare the right-hand chart with the bold lines on the Canon chart, and remember to read between the Zeiss lines for Nikon/Canon comparisons):
Excellent performer stepped down, the Carl Zeiss 4/18 Distagon.
Essentially what the charts say is that wide-open even the Zeiss ZM has a hard time with corners, but stepped-down it picks up and draws pretty evenly across the entire frame. This is essentially what I’m hoping the new ZF will do. In the past they’ve been about 50/50 with their 18mms however, the Contax version wasn't this good.
Lastly, the new lens looks to be a pretty typical optical design for this range. In comparison the Nikkor has just one less element, and looks pretty much the same.
I’ll write again when the MTF chart comes out.