The inverse square law applies to point light sources or Fresnel lights and focusing lights:
Double the distance – one quarter of the light.
When the light source is close to the talent, this will produce the effect of changing light intensity as soon as the talent moves closer to the light source or further away.
In order to overcome these effects, we have several ways and thoughts:
1 – Place the light source far away from the talent, thus minimizing the relation between the actual distance covered by movement of talent and the change of light intensity.
When lighting indoors, there may be limitations, as to how far away you can place the light source.
2 – Indoors, with space limitations, you can use a hard reflector on the ceiling to create a larger distance between light source and your talent.
Please be aware, that with soft reflectors this effect cannot be achieved.
3 – The narrower you can spot your focusing light, the more you are creating a virtual light source, which is behind the actual light fixture, thus increasing the active distance between the virtual light source and your talent, which also minimizes the effect of intensity change caused by talent movements.
4 – Using a parallel light, the virtual light source is effective very far behind the actual light fixture – see pages 14-15, overcoming most of the ill effects of the square law.
5 – For focusing lights, Fresnel lights and such, you can use half scrims or graduated scrims to minimize the unwanted effect of the square law.
6 – We are the only ones who offer graduated grey filters for light fixtures, which also work wonders to eliminate the ill effects of the square law.
7 – For large areas of light emission, be it soft lights or large light-reflecting surfaces, the square law becomes less active at close proximity.
The lower effect of the square law may hold true, until the object or the person being lit is further away than two or three times the diameter of the light-emitting area.