Canon FD 50mm f/1.2 S.S.C.

Pull this one off an FTb or an old F-1 and open it all the way and it does exactly what you bought it for. Wide open at f/1.2 the Canon FD 50mm peels a face off the wall behind it, the background dissolving while the eyelashes stay just sharp enough to read as in focus. The S.S.C. coating (Super Spectra Coating, Canon's multilayer coating from the early 70s) is a real part of why these still trade hands fifty years on. It handles backlight better than its own f/1.4 siblings and better than most fast glass of its era.

The character at f/1.2 is both the appeal and the catch. There is real spherical aberration left wide open, so you get a glow, a slight veiling softness on specular highlights that softens skin and tanks resolution. People love it for exactly that. Shoot a portrait against streetlights and the out of focus points bloom into big discs with a faint bright rim. Stop down to f/2 and the glow burns off. By f/4 it is genuinely crisp across the frame, and from f/5.6 to f/8 it turns into a clinical, contrasty standard lens that will out resolve plenty of modern fifties.

It is a double-Gauss-type design, like almost every fast fifty of this period used, and Canon built it heavy. Brass and glass, a real focus throw, a hard click at every full stop down to f/16. This was the fast pro normal in the FD system, part of the same family of large-aperture Canon standards as the FD 55mm f/1.2 and the aspherical FD 55mm f/1.2 AL. Documentary and available-light shooters bought it because it was among the fastest affordable normals that flared this little.

The honest weakness: corners wide open are mush, and there is noticeable focus shift as you stop down from f/1.2. Nail focus wide open, then close to f/2, and your plane of sharpness can drift backward. On a split-prism finder that is a working problem, not a chart footnote. Field curvature is in there too, so flat subjects fall off at the edges before the center does.

Today it sits in the affordable-cult tier. People cross-shop it against the New FD 50 1.4 (sharper, less magic) and against adapted Nikkor and Minolta fast fifties on mirrorless. Mirrorless bodies have a short flange distance, which leaves room to mount FD glass on a simple adapter with no corrective element in the path, and that is exactly why FD primes like this one stay popular for adaptation. People keep it for the rendering more than the numbers.

One metering note. You shoot this because you can open it all the way, and in a stairwell or a dim room you will be metering at or near f/1.2 in light that throws off any meter that averages the whole frame around a bright point source. Take the reading off the actual highlight you care about, set your Zone Light Meter to spot off the face, and let the shadows fall where they fall. At f/1.2 your exposure margin is thin, and half a stop in the highlights is the difference between a held portrait and a blown one.