When striving to capture truly expressive portraits, focusing on facial expressions may seem like the most effective approach, and it certainly can be. But there are a number of other ways to shoot evocative, emotional images totally void of any facial expressions. As a matter of fact, you don’t need to reveal the face of your subject at all to capture a telling portrait of them.
Over the years, I’ve collected a photographic arsenal full of expressive images of both clients and of my own family that were taken from the back. I never tire of capturing images using this unobtrusive approach. Whether it’s a quintessential "walking away" shot, the shape of my subject’s silhouette or them gazing out into a sweeping landscape, framing from the back is an unexpected and poignant way to tell a captivating visual story.
There are a number of ways to approach shots like these to use them to your greatest photographic advantage. Start by considering your motivation in shooting from this perspective and work to meet that motivation in your final product.

LET THEM LEAD
I find that shooting from behind while my subject is walking away from me is one of the least hands-on photographic approaches there is. This can make for an easy job of capturing your subject in an authentic way of just being themselves.
You do need to keep certain camera settings in mind, however. Because they’re in motion, you have to move along with your subject—depending on how much space you want to leave around them—so you may need to shoot with a faster shutter speed to minimize potential blur. You have to watch your aperture, as well. Shooting too shallow may mean they walk right past the focal plane.
As far as when to snap your shutter, you’ll want to watch for a moment that may speak of your subject. Maybe it’s the little skip in a child’s step or their hair blowing in the wind that you want to frame just so. Remember, the story relies on body language, gate or other subtle gestures that express the mood of the moment.