Low Distortion and Field Curvature. The Leica 21mm f/3.4 ASPH Super-Elmar-M for Leica M offers the least amount of distortion of any of the Leica 21mm options, and is arguably the best wide angle M-mount lens made. While its f/3.4 aperture doesn’t give you the most flexible low-light shooting options, its lack of distortion and field curvature make it ideal for architectural and landscape shooters.

Advanced Optical Design. Its metal screw-mount hood provides phenomenal flare resistance, and its combination of aspherical and anomalous partial-dispersion elements gives corner-to-corner sharpness at all apertures. It features Leica’s 6-bit coding for in-camera vignette correction with compatible Leica M-series digital cameras.

Built-In Finder Lines. Many people shoot with the 21mm estimating from the widest set of built-in finder lines, but others prefer an externally mounted viewfinder.