Here you can examples of Crown Thinning with before and after shots.
Crown Thinning is a technique used to reduce the density of the branching area of the crown of the tree. It is also undertaken using chain saws and pruning saws. By reducing the overall volume of branches that make up the crown, this process allows the wind to pass through the crown easier and thus resulting in less stress on the main stem of the tree. Crown Thinning does not affect the shape and size of the crown.