What 27mm at f/1.2 actually gives you
27mm 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. On the APS-C bodies it covers, it frames like 41mm would on full-frame.
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 490g (1.08 lb) it sits in the middle for handling: substantial enough to feel planted, light enough not to dominate the kit.
Filters are 67mm — worth checking against what you already own, since polarisers and ND filters at this size are reusable across any other lens sharing the thread. A dedicated aperture ring gives direct control without going through a camera dial, which mostly matters for video work.
Autofocus and stabilisation
Autofocus is driven by an STM 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.
