I have always tried many different lenses for Auora shooting .this time i bought a used Sigma 20mm 1.8 for about 200 dollars(really cheap) and i practice to find the infinity focus 1 week before my trip to Iceland.I was very pleased with the result.Its not the widest i would like to have and not the sharper wide open ,but to have the privilege to shoot at 1.8 means a really short exposure time ,lower ISO and cleaner image.