Canon EF 50mm f/1.0L USM

There is a club photographer somewhere right now shooting at f/1 with one of these, getting maybe a 200th of a second handheld in near-darkness, and watching the focus plane slide off the eyelashes between frames. That is the deal with the EF 50mm f/1.0L. It buys you a stop of light that almost no other autofocus lens on earth could deliver, and it charges you for it at every aperture you actually want to use.

Canon built it in 1989 to show off the brand-new EF mount, which dropped the mechanical aperture linkage in favor of electromagnetic control. Without that, a working f/1 autofocus lens is basically impossible. The front element is a slab of glass with a 72mm filter thread and a heft that surprises people the first time they pick it up. It stayed in the catalog until 2000, never cheap, never common.

Wide open it does not render like a normal fifty. It glows. Spherical aberration smears highlights into a soft halo, contrast drops, and the depth of field is so thin that a portrait at three feet puts the ears already out of focus. Some people hate that look and call it broken. Others chase it precisely because nothing else does it. The bokeh is enormous and creamy, with onion-ring texture in the discs if you look hard. Stop down to f/2 and it cleans up fast; by f/2.8 it is genuinely sharp, by f/5.6 it is excellent. But nobody buys an f/1 lens to shoot it at f/5.6.

The honest weakness is the autofocus. The USM motor is hauling a lot of glass against a paper-thin focus plane, so it hunts in the dark exactly when you need it most, and even a perfect AF lock can miss because the subject breathed. Manual focus through a film viewfinder at f/1 is its own act of faith. There is no trick that makes it reliable; most shooters just take a lot of frames.

Cross-shop is the easy part: there isn't much. The f/1.2L USM that replaced it (2006) is better corrected and focuses more reliably, though it has its own soft, character-heavy wide-open rendering, and it loses that last sliver of speed. The old screwmount and rangefinder f/1 oddities don't autofocus. So this remains a collector and specialist piece, prices climbing because Canon will almost certainly never make a 50/1.0 again.

If you do put it on a film body, meter wide open and trust the spec, not the rendering. At f/1 the haze and falling contrast can fool you into thinking the scene is darker than it is, so an incident or spot read into Zone Light Meter at the true working aperture keeps your shadows where you want them rather than chasing the glow. Then open all the way, accept the softness as the point, and shoot the thing it was built to shoot: a single lit face in a room that no other lens can hold.