I already posted photoshop tutorial about how to fix dark shadows from photographs u may check video post from here and i developed photoshop action also to it. in this video i show you how to use the action and it helps for photographers and designers for fix their photos.
first download action from below link and load it in action panel. Open photograph u want to fix and click play button. If u want effect only on face then u paint on mask with black.
Check before and after results: