Exercise #1: Inverse-Square Law

To demonstrate the inverse-square law, I set up two cameras and one light source in the studio. I used the hot light to light the subject [Nikon D5000] while I photographed the subject with the Nikon D850. From my understanding of the inverse-square law, each time we double the distance from the lens to the light, we need to expose two stops more to accommodate for the falloff.

In the photographs made by the D850, it's clear to see the darkest shadows opening up more the further the small light source gets, as shown by the shadow clippings in Lightroom below.

In the photographs of the light source made by the Nikon D5000, it's apparent that the light source is getting 75% smaller, and consequently, we are left with 25% of the light from the previous shot. To accommodate for this loss of light, we need to let in twice as much light.

One thing that surprised me was the jump from 8 feet to 16 feet. In the photograph of the subject at 8 feet, the background is still hardly visible, mostly dark shadows. At 16 feet, the background, although still dark, is almost completely visible.