Canon EF 85mm f/1.2L USM

Wide open at f/1.2, the plane of focus on this lens is so thin that an eyelash can be sharp while the iris behind it goes soft. That is the whole reason people put up with everything else about it. The out-of-focus rendering is round, smooth, and almost liquid, with backgrounds that dissolve into color rather than detail. Skin glows. There is a faint veiling haze at full aperture that some shooters chase on purpose, because it flatters faces in a way no sharper lens can fake.

Canon built this around a big front group with an aspherical element to wrestle that f/1.2 aperture into something usable, and the trade is mass and speed. The thing is heavy and front-loaded, and the autofocus is slow. The whole front cell physically moves to focus, driven by the ring USM motor, so it hunts and lumbers in a way that feels ancient next to a modern lens. Catch a toddler running at you wide open and you will miss most of the frame. That is not a bug you fix in software. It is the price of the glass.

Stopped down to f/2 and f/2.8 it tightens up and the contrast climbs, but almost nobody buys an 85 f/1.2 to shoot it at f/4. This is a wide-open portrait tool first and a general lens a distant second. Wedding photographers shooting available-light receptions love it. So do editorial portrait shooters who want a single environmental frame where the subject floats off the background. Across the EF era it was the aspirational fast 85, cross-shopped against the cheaper, faster-focusing 85mm f/1.8 that most people actually bought, and against the f/1.4 lenses from Sigma and others that came later with better autofocus and lower price. People still hunt down this version because the f/1.2 look does not have a true substitute.

The honest weakness, beyond the focus speed, is longitudinal chromatic aberration. Wide open you get green and magenta fringing on specular highlights, the bright rim of a backlit hairline or chrome trim. It is real and it is visible at 100 percent. Stop down a hair and it cleans up, but at f/1.2 you live with it.

One metering note for film shooters running this on an EOS body. At f/1.2 in dim window light or a candlelit room, meter for the shadow you care about and place it where you want it, because the whole point of buying this aperture is shooting where there is barely any light. Drop your reading into Zone Light Meter and put the subject's shadow side on Zone IV or V; the lens gathers the rest. The 72mm thread is also a clean, common size if you want to stack an ND to keep f/1.2 in daylight without blowing past your top shutter speed.