The natural, backlit look is a highly popular style among wedding and portrait photographers that many clients are quite fond of. This great tutorial will give you some helpful tips for taking better backlit portraits.
Coming to you from Julia Trotti, this helpful video talks about some useful tips for backlit portraits. If you're a fan of that light and airy natural look, it's likely you're thinking of this type of shot. Shooting backlit tends to reduce contrast, which is what creates that style. It also tends to render your subject more softly, as there is no direct light on them, which in turn reduces the appearance of contrast and texture on their skin. Of course, the problem with this is that you often end up underexposing your subject to protect the highlights in the background. As Trotti mentions, look carefully around your shooting environment for any sort of broad, light object that can kick back light toward your subject. Something like a white wall will act as a large light source, keeping the soft look you're going for while adding a bit of fill on your subject. Check out the video above for more!
I was rather curious why Julia used the widest aperture available. So, not being a full-time portraiture photographer, I googled and came across this article: https://www.photoshopactions.com/blogs/blog/how-to-shoot-with-backlighting.