What 4mm at f/2.8 actually gives you
At 4mm this sits in ultra-wide territory, where straight lines near the frame edge stretch noticeably and a small step forward changes the composition a lot. On the Micro Four Thirds bodies it covers, it frames like 8mm would on full-frame.
f/2.8 is the working standard for a fast lens — a stop or two of low-light headroom over a kit zoom, and noticeably more background separation.
Size and close focus
At 85g (3.0 oz) it is light enough that it stops being a decision — the kind of lens that stays on the body or in the bag without thought.
It focuses to 12cm, which is close enough to fill the frame with small subjects.
Manual focus and stabilisation
Focus is manual only. That suits deliberate work — landscapes, macro, video pulls — and rules it out for anything that moves unpredictably.
There is no optical stabilisation in the lens, so handheld steadiness depends on the body having IBIS, or on keeping the shutter speed up.
