When I take portraits outside in sunlight I try as much as I can (but not always, of course) to have the model with the sun in her back, just to avoid harsh shadows from strong sunlight. With his/her back to the sunlight, you often also get the benefit of free hair light and rim light, that separates your model a bit from the background. Even if you shoot with a short DOF, it is nice to have that. I think.
Last year when I was on an assignment for a Swedish book publisher to shoot some pictures for new book covers, the theme this time was books about girls and horses. So, I went to a small town were the author lives and together with some horses and a girl that would model as the books main character, we took portraits and action photos all day.
One of the photos they selected for one of the covers was the one above, and it was pure coincidence that the horse in this photo was white. Lucky me.
Standing so close to the girl, the white horse were not just a model in this photo, but also a reflector. The white skin/hide (?) reflected the strong sunlight from the back and gave a nice sheen to the girls face, that would have been in the shadows otherwise.
So, it is good to have a white horse around if you don’t have an assistant 🙂