The Voigtlander 21mm f/1.8 Ultron is a fast aperture wide angle lens for Leica M-mount cameras. The lens offers rangefinder-coupled focusing from 0.7m to infinity, with an additional close focusing option down to 0.5m using the hyperfocal distance method. The fast f/1.8 aperture allows you to capture images with a shallow depth of field, providing smooth background blur for true subject isolation.
The sturdy metal build quality is very high, with a smooth, long throw focus ring and half-stop aperture clicks for minute adjustments. It features a built-in petal hood to help minimize lens flare, and its 11 group / 13 element optical design with one aspherical element keep optical aberrations at bay.
Many people shoot with the 21mm estimating from the widest set of built-in finder lines, but others prefer an external mounted viewfinder.