About Leica 21mm f/3.4
To meet the requirements of digital photography, the Leica Super-Elmar-M 21mm/3.4 ASPH is a benchmark in all optical performance characteristics. The stray light optimization was implemented on a very high level, allowing for backlit shots with crystal clear contrast. The design of the metal lens hood matches the appearance of the current wide-angle lenses of the Leica M system. This lens hood is also compatible with the Leica Super Elmar-M 24 mm/3.8 ASPH and the Leica Super Elmar-M 35mm/1.4.
With the Leica M8 and M8.2, the Leica Super-Elmar-M 21mm/3.4 ASPH has an equivalent focal length of 28 mm making it a practical standard wide-angle lens for use with the Leica M8 and M8.2.