What 50mm at f/1.2 actually gives you
50mm sits close to the way the eye takes in a scene, which is why this range tends to get used as a general-purpose focal length.
The f/1.2 maximum aperture is about as fast as production lenses get: it gathers a lot of light and throws backgrounds well out of focus, at the cost of a depth of field thin enough that focus accuracy starts to matter on close subjects.
Size and filters
At 950g (2.09 lb) it has real presence on the front of a camera, though it stays hand-holdable for a session.
Filters are 77mm — worth checking against what you already own, since polarisers and ND filters at this size are reusable across any other lens sharing the thread.
Autofocus, stabilisation and weather sealing
Autofocus is driven by a Ring USM motor.
There is no optical stabilisation in the lens, so handheld steadiness depends on the body having IBIS, or on keeping the shutter speed up.
The barrel is weather-sealed, so rain and dust are a manageable risk rather than a reason to pack up.
