What 42mm at f/1.2 actually gives you
42mm 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 Micro Four Thirds bodies it covers, it frames like 84mm 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 425g (15.0 oz) 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.
Autofocus, stabilisation and weather sealing
Autofocus is driven by a Stepping motor.
Optical stabilisation is built in, which stacks with in-body stabilisation on bodies that have it and does the work alone on bodies that do not.
The barrel is weather-sealed, so rain and dust are a manageable risk rather than a reason to pack up.
