Leica Elmarit-M 21mm f/2.8

Set it next to the Zeiss Biogon 21mm f/2.8 ZM and the case against the Leica is easy to make. The Biogon is the true symmetrical design, flatter field, lower distortion, and it costs a fraction of what Leica asks. The Elmarit-M is the retrofocus 21, and retrofocus buys it a longer back focal distance than the symmetrical Biogon, which is exactly why it carries more glass and more weight. That extra room was chosen for back focus and corner illumination, not for any SLR mirror it never had to clear. Worth knowing: that same retrofocus geometry is what lets this lens clear the swinging meter arm on an M5 or CL, the very thing the deep symmetrical Super-Angulons could not do, so it meters where the older fast 21s would not. People pay the premium regardless. Some of it is the badge. The rest is that the rendering, especially on color slide film from this era, has a warmth and a corner roll-off the clinically correct Biogon will not give you.

Get the lineage straight, because the draft you may have read gets it wrong. This is the third Leica M 21, the pre-ASPH Elmarit-M sold from 1980 through 1997. It follows the two Super-Angulons, the f/4 and the f/3.4, and it was the first 21 Leica opened up to f/2.8. The aspherical version that arrived in 1997 replaced it. Optically the pre-ASPH flatters black and white. Stopped to f/5.6 or f/8 it is crisp across most of the frame, with the kind of micro-contrast that lifts brick, peeling paint, and crowd texture off the negative. Wide open at f/2.8 the center holds and the corners go soft and a touch dim, which on an ultrawide is usually right where your subject sits anyway. Contrast runs high. Flare is controlled but not gone; aim it into a low sun and you will catch the odd ghost, so hood it.

The honest weakness is vignetting and corner falloff. It is real on film and worse on the newer digital M bodies, where the steep ray angles at the sensor edge throw color shifts the film never showed. On Tri-X or Ektachrome it just looks like the lens. On a sensor it becomes a correction you make in software.

Who reaches for one: documentary and street shooters who want a single ultrawide that vanishes into the bag, and architecture people who will trade a little distortion for rangefinder size. You frame with an external 21mm finder in the accessory shoe, because the camera's own bright lines stop well short of this wide.

Filters are the practical wrinkle. It takes a 55mm thread, a chunky front for an M lens, so budget for that size when you build out filters rather than assuming your smaller Leica wides will share. Either way, a grad ND earns its keep on glass this wide for holding a bright sky. When you screw one on, drop the filter factor into Zone Light Meter so the suggested exposure already accounts for the lost light instead of you doing the math at the shoreline. Today it sits in the used-Leica tier, above the Zeiss and Voigtlander 21s and below the current aspherical Super-Elmar. Buy it for the Leica wide-angle signature on film, when you do not need the corner-to-corner perfection of the modern glass. For an M shooter working in available light, it still earns its place.