The inverse square law is a fundamental principle in photography and lighting, stating that the intensity of light falling on a subject is inversely proportional to the square of its distance from the light source. In simple terms, if you move a light twice as far from a subject, the subject receives only one-quarter of the light's intensity. Conversely, halving the distance increases the light intensity fourfold.
Understanding the inverse square law is essential for photographers using studio lights, flashes, or any controlled lighting setup. It allows precise control over exposure, lighting ratios, and shadow falloff, helping to achieve consistent, professional-quality images while manipulating light creatively for portraits, product photography, or dramatic effects.