What 20mm at f/1.8 actually gives you
20mm is wide enough to take in interiors, landscapes and architecture without the pronounced edge stretching of an ultra-wide.
f/1.8 is fast enough to keep shutter speeds up in poor light and to separate a subject from its background clearly.
Size, close focus and filters
At 505g (1.11 lb) it sits in the middle for handling: substantial enough to feel planted, light enough not to dominate the kit.
It focuses to 20cm, which is close enough to fill the frame with small subjects.
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 Multi-focus Stepping 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.
