Leica Noctilux-M 50mm f/1 (v1, E58)

The honest comparison is the Summilux 50mm f/1.4 sitting one slot down in the same Leica catalog. The Summilux is the rational choice. It is sharper at every shared aperture, smaller, lighter, and it costs a fraction of what this lens does on the used market. The Noctilux f/1 buys you one full stop more light and a rendering nobody else makes. That is the whole pitch, and for the people who want it, that one stop is the entire point.

Wide open at f/1, this is not a sharp lens, and Leica did not pretend otherwise. The center holds detail on the plane of focus, but contrast drops, the corners go soft, and there is real focus shift to manage as you stop down. What you get in exchange is the falloff. Depth of field at f/1 on a 50 is paper thin, and the transition from sharp to blur is gradual rather than abrupt, so a face lifts away from the background instead of sitting pasted on top of it. Out-of-focus highlights render as large soft discs, slightly brighter at the edge, with a faint cat's-eye stretch toward the corners from mechanical vignetting. By f/2.8 it tightens into a normal, very good Leica fifty. Most owners do not buy it to shoot at f/2.8.

The optical formula is a double-Gauss design pushed about as far as glass and a no-aspherical-element budget would go in the mid-1970s. This first version takes a 58mm filter (the E58), and the later f/1.0 carries a 60mm thread (E60). Filter size alone is not a clean tell against the f/0.95 ASPH that replaced the line, since that one is also E60, but it separates this v1 from the second f/1.0 cleanly enough. The big front element is why flare control is only fair. Point it at a streetlight or a bright window edge and you will see veiling haze and the occasional ghost. Some shooters chase that look on purpose for night work.

Available-light and night portrait people use one. So do wedding shooters who want a single frame no zoom can fake, and a certain kind of street photographer who likes shooting wide open in a bar at midnight. It is a slow, deliberate lens. The focus throw is long, focus at f/1 is unforgiving, and it weighs enough to feel it on the front of an M body all day. None of that has dented the price. These trade as collector glass now, cross-shopped against the modern f/0.95 ASPH and the various fast Voigtlander 50s that deliver clinical sharpness the Noctilux never attempts.

The honest weakness is that everything wide open is a compromise at once: sharpness, contrast, flare, and a focus shift that will burn you if you stop down without re-racking. You are buying a look, and the look comes with all of that attached. Working at f/1 in the dark is the only place this lens really makes sense, and that is exactly where a reflected reading goes unreliable, so meter the key light off your subject and use Zone Light Meter to place the face where you want it instead of trusting an averaged frame. Nail that placement and the rendering takes care of itself.