I took two buddies on a gravel ride last weekend. The video is posted on another page. Here's one photo of one of the buddies approaching the paved county road after a few uphill miles of dirt and gravel. It was a great day, the gravel portion was extra fun downhill in the opposite direction, and the most climbing he's ever done in his life.
Well, PS will do it! Back in the analogue days of the last century I used to use graduated and polarizing filters to get something like that, and then go into the darkroom. I couldn't wait for the days when I could do all of that on the computer (instead dark room full of chemicals).