The inverse square law is one of my favorite nerdy photography topics.
I use the inverse square law to get nice, dark backgrounds. I love this type of background because it leads to simple images, it hides my messy house, and it helps my subject really pop against a dark background.
The inverse square law has to do with light fall-off. The farther you are from the light source, the more fall-off you will have. However, the exact amount of fall-off is not really intuitive.
The quantity of light will be inversely proportional to its distance.
According to the law, the power of the light will be inversely proportional to the square of the distance. Therefore, an object that is twice the distance from a source of light will receive a quarter of the illumination (not half, as you might expect). Photographers who use artificial light need to understand this law to appropriately light their subjects. However, as natural light photographers we can use our knowledge of this law to perfect a technique for getting simple, dark backgrounds. We can utilize this law indoors, in our garage, and even outdoors.
If you want, you can ignore the boring math, but remember: the key to this technique is light fall-off. Light falls off increasingly over distance away from our light source.
Garage light is actually amazing for photos with black backgrounds. Don’t worry – your garage does not need to be neat and tidy! You want to place your subject in the shade but close to the line from the sun. So look for the line on your garage floor of where the light and shadow meet. Place your subject right inside the shade. Try a chair if you have a subject that moves constantly like mine do! (Bonus tip – I actually used a tricycle for this image below and let her sit on it!)
By placing your subject this way, you get nice light on their face, but the light falls off quickly and becomes very dark behind your subject. If it’s overcast or the sun is behind your house, you can simply place your subject right at the edge of where your garage meets your driveway.