Down lighting or "moon-lighting" as it is often referred to, is the art of creating the look of natural moon light passing down through tall, overhead trees and bathing the ground with soft light.  Down lighting can be very subtle as I just described or it can also be a bit brighter for more practical applications such as illuminating driveways and walkways from overhead.  The advantages of down lighting are that we can often reduce or eliminate path way lights that can sometimes clutter up the landscape and we can also bath larger areas in warm light using fewer luminaires.   The shadowing of leaves on the ground is really a cool effect and we try to incorporate it into our lighting designs when there is sufficient interest in the garden to merit it.