This image was treated in PS Essentials to reduce the underexposure of the underside of the bridge. Take the original image, change background to layer, duplicate the layer, go to the original layer and increase the wb to remove the underexposed portions (the correctly exposed portions will be over exposed now). Go back to the duplicate layer and erase the portion of the duplicate layer to reveal the, now, better exposed portion of the original layer. It seems to work fairly well. My erasing technique leaves a great deal to be desired. That will improve.