Thursday, January 24, 2008

The Inverse Square Law - Whaa?

What's the Inverse Square Law and why should I care? No one said there would be math - will it hurt?

This law of physics has extremely useful applications in video production. Understanding it will help you control your lighting and record better audio.

In Jay Rose's great book, Audio Postproduction for Digital Video he explains, "Each time you double the distance from a sound source, the power of the sound is one fourth as much. Each time you have the distance, it's quadrupled...It's called the inverse square law because power changes as the square of the change in distance." (page 26)

For example, if a microphone is four feet from your subject, moving the mic to a distance of two feet from that speaking subject will boost the power of that sound four times.

The same applies to light. Double the distance of your light from your subject and the intensity of that light decreases four times.

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