see also:
examples
the Olympus mZD 17mm f/1.8 lens or Panasonic Leica DG Summilux 15mm f/1.7 ASPH lens are reasonable choices
examples
is the Olympus mZD 25mm f/1.2 PRO lens one of the best?
alternatively, the Olympus mZD 12-40mm f/2.8 Pro weatherproof lens?