Light Falloff Node
The Light Falloff node allows you to manipulate how light intensity decreases over distance. In reality light will always fall off quadratically; however, it can be useful to manipulate as a non-physically-based lighting trick. Note that using Linear or Constant falloff may cause more light to be introduced with every global illumination bounce, making the resulting image extremely bright if many bounces are used.
Light strength before applying falloff modification.
Smooth intensity of light near light sources. This can avoid harsh highlights, and reduce global illumination noise. 0.0 corresponds to no smoothing; higher values smooth more. The maximum light strength will be strength/smooth.
Quadratic light falloff; this will leave strength unmodified if smooth is 0.0 and corresponds to reality.
Linear light falloff, giving a slower decrease in intensity over distance.
Constant light falloff, where the distance to the light has no influence on its intensity.
Todo <2.8 add.