One of my favorite lighting principles to share with young photographers and students is the inverse square law. That’s the physics principle that states that light falls off two stops for every doubling in distance from the source to the subject. I love this law, because it is an immensely useful. And it’s something I think most new photographers don’t think much about. But once they understand it, the sky is the limit in terms of how they can apply it to their advantage—changing the brightness of a background, for instance, simply by moving the key light. Anyway, the point is, I love the inverse square law, so I’m happy to pass along to you this inverse square law primer from DPS. It includes a simple graphic that shows exactly how the law functions photographically, as well as a good explanation of how you can apply it to your own work. Once you get the hang of the intricacies of light falloff, a whole new world of lighting will open up to you.