Canon EF 50mm f/1.4 USM

Wide open, this lens glows. There is a soft halo around bright edges, contrast drops, and the focus plane feels more suggested than locked. That is spherical aberration doing its thing, and it splits people: some chase that first-stop softness, others want it gone. Stop down to f/2 and most of the glow burns off. By f/2.8 it is sharp, and by f/4 to f/5.6 it is genuinely excellent across the frame. The whole personality lives in that first stop and a half.

Canon released it in 1993, the first autofocus 50mm f/1.4 for the EF mount, carrying forward the optical concept of the manual-focus FD 50mm f/1.4. It has stayed in the lineup essentially untouched for three decades. The USM here is the micro-motor type, not the ring-USM you get in the L primes, so autofocus is quick but a little buzzy and the manual override is fiddlier than you want. The eight-blade aperture gives reasonably round out-of-focus highlights, though stopped down they take on a slight polygon shape. Bokeh is smooth in the background and can get a touch nervous in the foreground, the usual double-Gauss compromise.

For portrait shooters on full-frame this has been the default 50 for years. It renders skin with that slightly low-contrast wide-open softness that flatters faces, then tightens up the moment you need it to. On an APS-C body the 80mm-equivalent field makes it a tidy short telephoto for headshots. Documentary and event photographers liked it because it gathers light in a dim room and the autofocus is fast enough to keep up, and it weighs almost nothing compared to the f/1.2L.

The honest weakness is the focusing mechanism. The unit-focusing helicoid that drives the whole optical group is the weak point, and a knock to the front can deform it. When that happens, an internal sleeve with diagonal cam slots bends, and AF sticks or stops working entirely, often near the close-focus end. The body shows no error code for it; the lens just refuses to move. This is not a tank. Treat it gently and it lasts; abuse it and the front group binds up.

The lens lives between two cheaper-and-pricier neighbors now. The EF 50mm f/1.8 STM gives you most of the sharpness for a fraction of the money, and the f/1.2L gives you the dreamy rendering with build quality to match. People still buy the f/1.4 for the gap it fills: faster and better-built than the nifty fifty, far cheaper than the L. On film, mounted to an EOS body, that extra stop over f/1.8 is the reason to own it. Metering wide open in a dark venue, set Zone Light Meter to f/1.4 and read the shutter speed it hands you; the 58mm thread takes a standard ND or polarizer when you want to shoot it open in daylight without blowing out the frame.