Leica Summicron-M 50mm f/2 (v4)

Walter Mandler drew this lens at Ernst Leitz Canada in Midland, Ontario, and the optical formula went into production in 1979. Mandler designed something like 45 lenses for Leitz, and he also wrote the definitive study on the limits of the double-Gauss layout. This 50 is that math made physical: six elements in four groups, the symmetric Planar-style arrangement that every serious 50mm has used since the 1950s, executed about as well as anyone has managed it. The optics have barely changed in over four decades. The formula dates to 1979 and the current barrel arrived in 1994, which is why a copy bought today reads as a mid-90s lens with late-70s glass inside it. The version with the focus tab and the 39mm thread is the one that has put more frames through more rangefinders than any other Mandler lens.

Wide open it is sharp in the center with a slight veil that collectors call the Leica glow, a low-contrast bloom around highlights that softens skin without smearing detail. Stop to f/4 and it snaps into clinical territory across the frame. The reason people guard their copies of this particular generation is the out-of-focus rendering. This is the 50 that built the smooth-rendering Leitz reputation. The background goes creamy and rounded with an eight-blade diaphragm holding the aperture nearly circular, and the falloff from sharp to soft is gentle instead of abrupt. It dissolves a busy backdrop into something you stop noticing, which is exactly what you want behind a face.

The honest weakness is harsh light. Point it into the sun or shoot strong sidelight against a busy background and the bokeh can get nervous, with visible outlining on specular points until you close to f/2.8. Flare resistance is decent for a design this old but it is not modern multicoating; you will want a hood when the sun is in the frame. And it is contrast-modest by current standards, which reads as character on film and as flatness to anyone raised on the ASPH.

This is a documentary and portrait lens first. Street shooters love the tab because you can pre-focus by feel without looking down, and the f/2 speed is enough for available-dark work in a bar or a doorway. It is not a landscape specialist; corner performance wide open is the price of the glow. The rival is the newer Summicron-M ASPH, which is sharper and more clinical and flatter in rendering, and the eternal argument is whether you want correctness or that older Leitz signature. People keep buying this one because the signature does not come back once you give it up.

For metering, the payoff of f/2 is low-light handheld work, so meter wide open and trust the speed. Run an incident or spot reading in Zone Light Meter at the actual taking aperture rather than guessing a stop down, because with this lens you will often be shooting at f/2 in light where half a stop decides whether the shadows hold. The 39mm thread takes standard E39 filters if you want a yellow for black and white skies or an ND for daylight wide-open portraits.