Its bright aperture for a 90mm lens makes for faster shutter speeds in dim light—great for street shooting and much more. Focusing ring could be made with a tad more grippable material.
Standout Spec: Light falloff—none whatsoever.
Leica Tri-Elmar-M 16–18–21mm f/4 ASPH
Leica 90MM F/4 Macro-Elmar M
Leica Noctilux-M 50mm f/0.95 ASPH
Leica Summicron-M 50mm f/2