Canon FD 24mm f/2 S.S.C.

Canon built this one to shoot a 24mm wide open when the light runs out. f/2 at 24mm was a fast maximum aperture for a wide of its day, less common than the slower 24s everyone else was making, and Canon held it together with an 11-element, 9-group design and a floating-element system (their Floating System) that adjusts correction as you rack the focus. That floating group is what keeps the close-focus performance honest and stops the edges from falling apart the way a fixed retrofocus design of this speed tends to. It is a spherical design, not the ground-aspheric f/1.4 it sometimes gets confused with, and it earns its reputation the hard way.

Wide open at f/2 you get a sharp center and corners that go soft and slightly smeared, with a faint glow on point highlights. Some shooters lean into that glow, others stop down to kill it. Bring it to f/5.6 and the frame tightens edge to edge into something you would trust for architecture or a landscape. The S.S.C. multicoat (Super Spectra Coating, Canon's coating of the era) keeps contrast respectable into the light, though a fast 24 will still throw the occasional flare or ghost if you aim it straight at a streetlamp. Field curvature is mild. Distortion stays well controlled for a retrofocus wide this fast.

The rendering is why you reach for it over the cheaper, smaller FD 24mm f/2.8, which generally cleans up well in the corners. The f/2 is for the person who needs the extra stop. Indoors, at concerts, on a dim stairwell or a night street, that stop is the whole job. The falloff into the out-of-focus background, while no bokeh showcase at this focal length, stays smooth and untextured, and the draw feels more atmospheric than the f/2.8's flatter, more literal look.

Mount it on a film FD body, or adapt it to mirrorless, where the short flange gap makes FD glass easy to work with. The 55mm filter thread is shared across the fast FD primes, so one set of ND or polarizers covers it alongside the 50mm f/1.4 and the 35mm f/2. Working it wide open in low light, meter off the actual aperture you mean to shoot. In Zone Light Meter that f/2 reading places shadow detail several stops lower than the slower 24 would, so your shutter carries the load. Watch the slow end for handheld shake.

The honest weakness is the corners at f/2. If you need an even frame at maximum aperture, look elsewhere, and a clean copy will cost you. The f/2 sells above the f/2.8 because it is the faster, less common variant, not because of any exotic element. Cross-shopped against the Nikkor 24mm f/2 AI and the field of adapted-to-mirrorless options, the Canon keeps its spot on the strength of that fast spherical draw and the floating-element steadiness across the focus range. People still buy it because of how it renders in the dark, soft corners and all.