In 2011, Leica expanded their selection of super wide angle lenses for the M system by introducing the Super-Elmar-M 21 mm f/3.4 Asph. The lens was distinguished by its combination of outstanding reproduction performance and a compact design. Its specifications resembled those of Leica's legendary Super-Angulon 21 mm f/3.4, which had been produced from 1963 to 1980.
Vignetting, which is inherent in every optical system, naturally becomes more pronounced in super wide angles than it is in normal or long focal length lenses. At full aperture in small format, vignetting appears in the corners of the image at around 2.1 stops. With the somewhat smaller format of the M8 models, it occurs at around 1.2 stops. Stopping down to f/5.6 reduces this light fall-off at the edge of the image to 1.6 and 1.0 stops respectively. There is little to be gained from stopping down any further, as only the natural vignetting remains.
The lens offers a maximum – almost imperceptible – distortion of just 1.5%. Its retro-focus design comprises eight elements. One element features two aspherical surfaces, while four elements are made of glass types with anomalous colour dispersion (partial dispersion) – all of which is instrumental in restricting optical aberrations.