I don't understand the obsession with lightness. In my opinion it is a red herring. In all cases you will need a very sturdy tripod, and that will weigh more than your camera by several kilos. With a lens that will weigh a couple of kilos on top of that, the difference in the main body weight of 1kg or so between brands/models is irrelevant. Wherever you take it..it will be an effort...K