some time ago on a rainy day I was a little bit bored and decided to do a little comparison over the entire ISO range of the M9. On the left you see shot wide open @1.4 and on the right @5.6. This is in no way a scientific test. (Lens used: Summilux 50 1.4 ASPH)
Just click the little kitties to see the full size crop of them.