Leica Noctilux-M 75mm f/1.25 ASPH

Wide open, this lens puts a single eyelash in focus and lets everything a centimeter behind it dissolve. That is the whole pitch. At f/1.25 the depth of field on a 75mm lens is paper, and Leica built the Noctilux-M 75mm to make that paper sing rather than smear. The plane of sharpness is genuinely crisp, with real micro-contrast on the eye, while the falloff into defocus is gradual and rounded instead of nervous. Specular highlights come back as soft discs, not the cat-eye footballs you get from cheaper fast glass clipping at the edges.

It arrived in 2017 as the second modern Noctilux, the longer sibling to the 50mm f/0.95. Aspherical surfaces and a floating element keep aberrations under control at full aperture, which is the hard part on a lens this fast at this focal length. There is a faint glow wide open that some shooters love and that clears up immediately by f/2. Color is neutral and the rendering reads as dimensional in a way that flatter modern portrait lenses do not, the subject lifting off the background without a halo.

Who buys it: portrait and wedding shooters working on M bodies who want the most aggressive subject isolation Leica makes at 75mm, plus collectors who want every Noctilux on the shelf. It is a deliberate, slow-handling tool. You focus, you recompose carefully, you accept that a chunk of frames at f/1.25 will miss because the rangefinder patch simply cannot resolve that thin a plane reliably. People who shoot it wide open a lot end up adding a Visoflex or moving to an SL body for focus confirmation.

The honest weakness is the package. It is roughly a kilogram of glass and brass hanging off a small rangefinder, front-heavy and conspicuous, and the price sits in five figures. The 67mm front is large for an M lens. If you want 75mm sharpness without the bulk or the cost, the APO-Summicron-M 75mm f/2 is the lens most people cross-shop against, and it wins on resolution and handling while losing the extreme blur. You pay the Noctilux premium for that last stop and a third and the look it buys.

One practical note for using it. At f/1.25 you are usually shooting in the dim conditions that justify a lens this fast, so meter at working aperture in Zone Light Meter and trust the wide-open reading; the difference between f/1.25 and f/1.4 is real exposure that an external meter rounded to whole stops will miss. The 67mm thread takes a standard ND if you want to hold that aperture open in daylight without slamming into the shutter ceiling. Stop down past f/4 and it behaves like any sharp normal-tele, but nobody buys this lens to shoot it at f/8.