A uniquely versatile super-wide lens, the Tri-Elmar-M 16-18-21mm f/4 ASPH. from Leica allows you to work with three separate focal lengths within one lens. The optical design, which includes a pair of aspherical elements, notably reduces distortion for clean, accurate rendering of interior and architectural subjects, and the aspherical elements also promote a more compact form factor. Seamless switching between 16mm, 18mm, and 21mm focal length positions is possible while retaining a minimum focusing distance of 1.6', and a floating elements design is used to maintain image quality even at close range.

The Leica Universal Wide-Angle Viewfinder M is a shoe-mounted external viewfinder for M-system rangefinder cameras (including M8). This viewfinder offers bright-line frames to match the 16-18-21mm lens. Since the 1.33x conversion factor has to be considered for the M8 digital camera, bright-lines for 21, 24, and 28mm are also included. It can also be used with other fixed lenses that match this range. A parallax compensation dial allows for adjustment of the frame to the focusing distance, in five steps (0.5, 0.7, 1, 2 meter & infinity).

The use of one aspherical lens element and one with achromatic correction in the viewfinder makes it insensitive to stray light, and provides a high resolution and exceptional brilliance image.