Had an outing last night shooting in very low light (See samples below). I started out with Panny 20mm (on E-PM1) and couldn't get ONE picture in focus and for most of the scenes I couldn't get a focus lock at all. It was a total nightmare until I switched to Panny 14mm and it was like a miracle, instant, accurate focus for over 300 pics. All perfectly in focus. I've owned Panny 20 for a while and I know it is a slow focusing lens but this was my first experience shooting with it in such low light for a prolonged period of time. The problem wasn't even slow focus but the fact that I couldn't get a focus lock for most of the scenes. AF assist light had no effect. Based on my experience I can't recommend Panny 20 for low light to anyone. It's ironic because the lens has bright f1.7 aperture yet it's possibly the worst lens to use in low light among all m43 lenses. Panny 14mm is a gem. I am especially impressed that changing aperture didn't affect focus speed at all, both f2.5 and f4 are same AF speed and both accurate.