What is the inverse square law in photography?

The inverse square law is a principle in physics that applies to many different fields, including photography. In photography, the inverse square law states that the intensity of light decreases in proportion to the square of the distance from the source of light.

In other words, if you move your subject twice as far away from your light source, the intensity of light on your subject will decrease by a factor of four. This means that you'll need to increase your exposure by two stops to compensate for the decrease in light.

The inverse square law is important to understand in photography because it can affect the way you position your lights and how you expose your images. By understanding how light falls off over distance, you can create more balanced and pleasing lighting in your photographs.

Here’s a great example.

Let's say you're using a flash to light a subject, and the flash is positioned one meter (approximately three feet) away from the subject. According to the inverse square law, if you move the flash back two meters (approximately six feet), the intensity of light on the subject will decrease to one-fourth of its original value (since 2 squared is 4).

To compensate for this decrease in light intensity, you'll need to increase your exposure by two stops. This means that if your original exposure was f/8 at 1/125th of a second, you'll need to adjust it to f/4 at 1/125th of a second to get the same level of exposure on the subject.

By understanding the inverse square law, you can make more informed decisions about the placement of your lights and how you set your camera's exposure settings to achieve the desired lighting effect on your subject.

More to come on this subject so stayed tune…