The Voigtländer Ultron 28mm 2.0 is a quite small wide angle lens with Leica M mount. You may look up the specifications here on the official homepage. The lens is a quite modern design and has been introduced around 2012.
It is one of my favorite lenses on the A7s. Phillip read my reports about it and asked me whether I would like to write an in-depth review about it. Hopefully, at the end of this review, you will know why I like the Voigtländer 2/28 so much.
A German version of this review can be found on phillipreeve.de.