Wow impressive stuff! I know Samaras has been doing this for a few years now and he did a talk on it a the chaser con in Denver a few years back. It is a very large (must be hauled with a trailer) and very expensive slow motion camera. I forget how many frames per second but something crazy like 10,000fps or something. Something I remember him noting is all of those little leaders going all while the lightning was occuring up in the cloud base. It is amazing how even at 10,000fps the leaders seem to be flashing at a rate similar to a typical lightning strike in real time.