This filter can be added to all Arnold Lights. This is where you will specify the attenuation ranges. All lights in Arnold use a physically-based falloff by default, but the light_decay filter can be used to adjust the falloff for artistic purposes.
The Near Attenuation value sets the distance at which the light intensity "fades in". It works like a reverse decay. The light does not shine from the source to the Start range of the Near Attenuation then increases brightness until the End range of Near Attenuation.
The Far Attenuation value sets the distance at which the light "fades out". It works like a normal decay, but you can specify the start and end distance. The light diminishes from the Far Start range to the Far End range using a smooth ramp between.
The distance at which the light begins to fade in. ie, 0 = light source.
The distance at which the light reaches its full value.
The distance at which the light has faded out to 0.