Head to head
Canon FD 50mm f/1.4 S.S.C. vs Leica Summilux-M 35mm f/1.4 ASPH
Two fast primes that keep landing on the same shortlist, mostly because they promise the same thing: a bright finder, shallow depth of field, and that classic full-frame "normal-ish" look wide open. The honest gap between them is not optical, it is the system. The Canon is a 50mm SLR lens that mounts on FD bodies and costs about as much as a tank of gas. The Summilux is a 35mm rangefinder lens for Leica M, and it costs more than most people's entire camera kit.
How they differ
Focal length changes how you shoot before anything else. The Canon 50mm sits in tight, flatters faces, and isolates a subject without effort. The 35mm Summilux pulls back to a reportage field of view, so you work closer, take in more room, and lean on the rangefinder's framelines instead of a through-the-lens image. One is an SLR experience (you see exactly what the sensor or film sees, including the focus falloff), the other is the quiet, no-blackout rangefinder flow that a lot of street and documentary shooters never give up.
Rendering and build pull in opposite directions too. The FD 50 f/1.4 is a little soft and glowy wide open with warm rendering, then snaps to genuinely sharp by f/2.8, and it flares more against bright light, which some people chase on purpose. The aspherical Summilux is corrected hard: high contrast and biting detail from f/1.4, controlled flare, and a more clinical, modern signature. Cost and supply are the loudest difference. Clean Canon copies are cheap and plentiful (you'll find them constantly), while the Leica is a small fortune, often back-ordered or sold used at a premium, and the FD lens needs an adapter to live on most modern bodies.
Choose Canon FD 50mm f/1.4 S.S.C.
Pick the Canon FD 50mm f/1.4 S.S.C. if you want a fast normal lens on a budget, shoot portraits or close subject isolation, and like a slightly vintage, warm look wide open that cleans up by f/2.8. It's the right call for FD film shooters and for anyone adapting glass to mirrorless who wants character without spending much. Great first fast fifty.
Full Canon FD 50mm f/1.4 S.S.C. guide →Choose Leica Summilux-M 35mm f/1.4 ASPH
Pick the Leica Summilux-M 35mm f/1.4 ASPH if you already shoot the M system (or are committed to it), want a wider documentary field of view, and need biting contrast and detail wide open for street, reportage, and low light. It suits photographers who value the rangefinder workflow and small size, and who can justify the price for a lens that holds its quality and its value for decades.
Full Leica Summilux-M 35mm f/1.4 ASPH guide →The verdict
These barely compete on rendering because they are different focal lengths in different systems. If money is the deciding factor, the Canon gives you most of the fast-prime joy for a fraction of the price. If you're an M shooter who wants a 35 that's flawless wide open, the Summilux earns its cost. Match the focal length to how you actually frame, then let the budget decide.