APO-Summicron-M 50mm f/2 ASPH

When Leica released the APO-Summicron-M 50mm f/2 ASPH in 2012 at $7,195, independent optical bench tests quickly produced a remarkable verdict: this was the highest-resolving 50mm lens ever measured for any camera system. "APO" stands for apochromatic — the lens is corrected for chromatic aberration across three wavelengths rather than the usual two, meaning colour fringing is essentially absent even at the pixel level on high-resolution sensors.

For beginners: the difference between an APO lens and a conventional lens is most visible in fine detail — text on signs, individual hairs, fabric weave. On a 24MP M10 the APO-Summicron delivers results that previously required a medium-format system. It is also, paradoxically, a much more neutral-looking lens than the vintage alternatives: no glow, no swirl, no character aberrations. Photographers who want a Leica for film-era rendering buy something else; photographers who want the absolute optical limit buy this. Used prices hold within 20% of new.