Leica Elmar 50mm f/3.5 (LTM, collapsible)

Max Berek computed it in Wetzlar in the mid-1920s for a camera nobody had asked for. Oskar Barnack's Leica was built around a strip of movie film, and it needed a lens small enough to match, something that could collapse into the body so the whole package slid into a coat pocket. The earliest Leica I shipped with Berek's five-element Anastigmat, soon branded Elmax, but the simpler four-element Elmar quickly took its place and became the standard optic through the I, II, and III. It was the lens that argued a 35mm negative could be enlarged into a real photograph at all.

The formula is a Tessar type, four elements in three groups. Leitz put the diaphragm up front, so you set the aperture with a tiny tab you nudge with a fingernail instead of a proper ring, which is usually the first thing that tells you you are holding an Elmar and not a copy. Wide open at f/3.5 it draws with low contrast and a soft halo on highlights, and the prewar uncoated versions flare into milk if you aim them near the sun. Stop down to f/8 and the center goes genuinely sharp, corners catching up by f/11. Postwar coated examples hold contrast far better.

This is the 50mm generation Henri Cartier-Bresson came up on. He got his Leica around 1932, when the f/3.5 Elmar was the standard normal lens, before the faster Summar f/2 and later the Summicron, so the look in those early prints is very much this kind of glass: gentle gradation, a soft signature wide open, gradients that fall away instead of snapping. It reads on faces and on rough street texture the same way, never clinical.

The weaknesses are honest ones. f/3.5 is slow, so this is no low-light tool, and it focuses no closer than a meter, which rules out tight portraits. The 19mm filter thread is a scavenger hunt of its own; most shooters give up and use A36 push-on clamps instead. The front-tab aperture is genuinely fiddly when you are working fast.

Even so, it remains one of the cheapest ways onto real Leitz glass, and the obvious cross-shop is the Soviet Industar copies on FED and Zorki bodies, which clone the same Tessar math for a fraction of the money and most of the look. People pay the Leica premium for the build and the collapsing barrel as much as for the provenance. One field note: meter a sunny scene on 400 film and you will see why a slow lens still wants a filter. At f/3.5 the exposure runs well past a screw-mount Leica's 1/500 or 1/1000 ceiling, so when Zone Light Meter flags that overexposure it is your cue to thread on an ND, or to load slower stock if you want the wide-open glow in daylight.