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Inverse-Square Law: The Nerdy Term Every Photographer & Filmmaker Should Know

Caleb Ward

Learning the Inverse Square Law will help you understand lighting and how it is affected by distance.

As a photographer or filmmaker one of the most important lighting terms for you to remember is the Inverse-Square Law, a law stating that the intensity of an effect such as illumination or gravitational force changes, in inverse proportion to the square of the distance from the source. You got that, right?

Simply put, the inverse-square law states that there is an exponential relationship between the distance of your light and the amount of light hitting your subject. This means if you move a light from 1 meter away from your subject to 2 meters away, it will only have 25% of the light that was on your subject at 1 meter. If you move your light from 1 meter to 3 meters away it will only have 11% of the light that was on your subject at 1 meter. The same principle applies to any unit of distance. This phenomenon is represented by a surprisingly simple formula:

Learning the formula isn’t as important as simply understanding the concept….

In practical terms this means if you need more light, simply place your light closer to your subject and you will get exponentially more light. However, there is a trade-off that occurs when you move your light closer to your subject. When lights are far away they are more evenly distributed across multiple subjects or your background, but if you move the light towards your subject there will begin to be an uneven distribution in light. This works great if you are trying to isolate a single subject, but works terribly if you are wanting to shoot a group of people or light an entire scene.

The following videos created by photographer Karl Taylor explains the inverse-square law and how understanding it can help you understand lighting more fully as a photographer or filmmaker. The video covers:

  • Inverse-square law
  • Lighting group shots
  • Understanding distance vs light intensity
  • Isolating a subject from the background

If you are still interested in learning more about lighting check out our Lighting for Video series.

This video was first shared by Karl Taylor on his YouTube Channel. Thanks for Sharing Karl! If you want to check out more of Karl’s photography or tutorials you can check out his work at KarlTaylorPhotography.com.

Has the Inverse-Square Law helped you in any other ways? Share in the comments below.