Leica Summilux-M 50mm f/1.4 ASPH

Find a street shooter working a dark city at midnight with one body and one lens, and odds are good this is the lens. The Summilux-M 50mm f/1.4 ASPH is the fast fifty that working Leica photographers reach for when the light goes, because it does the one thing the old Summilux versions could not: it is genuinely sharp wide open. Shoot a portrait at f/1.4 in a bar and the eyelashes are crisp while everything behind the head dissolves. That was not true of the older 50 Luxes, and it changed what people expected from a fast normal.

This is the third generation, out since 2004, and it was the one where Leica dropped an aspherical element into the 50 Lux along with a floating element that shifts as you focus close. The pre-ASPH version had a soft, glowy look at f/1.4 that some people chased and some people fought. This redesign trades almost all of that glow for resolution and contrast. Center resolution is excellent wide open, with the corners tightening up as you stop down. By f/2.8 the whole frame is clinical. A few shooters still mourn the dreamy older rendering, but if you want crisp at f/1.4, this is the one.

The out-of-focus rendering is half the reason to own it. Highlights stay round and clean across most of the frame, the falloff from the focus plane is gradual and reads as depth rather than a hard cutoff, and you get very little of the nervous busy background that plagues cheaper fast fifties. Color is neutral and saturated, contrast runs high without strangling the shadows, and flare is well controlled for a lens this fast. You will still want to shield it from a bright source sitting just outside the frame. It does show some field curvature wide open, so the very edges of a dead-flat subject like a wall of text can drift out of the plane until you stop down.

Then there is the price, which is the real catch. This is one of the most expensive 50mm lenses on the market, and at f/1.4 the depth of field on a rangefinder is so thin that a calibration even slightly off gives you front or back focus you cannot recover in post. People cross-shop it against the Zeiss ZM 50mm f/1.5 Sonnar, which costs far less and leans vintage, and against Leica's own Summicron 50mm, which is smaller and optically superb but one stop slower. You buy the Summilux specifically because you need f/1.4 and refuse to give up sharpness to get it.

This lens earns its keep when you meter wide open in the dark, and that is exactly where a guessed exposure falls apart. The 46mm thread will take a small ND if you want f/1.4 in daylight, but the home turf is available light across the f/1.4 to f/16 range. Read the actual shadow you care about with Zone Light Meter in spot mode, place it on the zone scale where you want it, and let the thin depth of field do the rest. At f/1.4 there is no margin, so meter the face, not the room.