Spotlight
Renders an expanding beam of light between two control points.

Start The source point of the spotlight
End The end point of the spotlight
Extend Adjustment that extends/retracts the spotlight from/to its source.
Focus Focuses the light effect from a puff of light, to laser-sharp.
Falloff The amount of falloff from the Start to the End points
Color
Spotlight Color Manual: The colors are set manually, below.
From Start Point: The spotlight color is derived from the start point
From End Point: The spotlight color is derived from the end point
Blend Start to End: The spotlight color is a gradient between the start & end points.
Color Smoothing The amount to smooth color samples when not using Manual color mode.
Manual Color Sets the light color in Manual mode.
Background Color Sets the background color
Fog
Fog (Enable) Enables fog
Fog Type Sets the fog type. Choose from Normal or Streaks
Fog Thickness Controls the amount of fog affecting the spotlight.
X Scale Sets the horizontal fog scale, higher values yield smoother animations
Y Scale Sets the vertical fog scale, higher values yield smoother animations
Scaling (Link Y to X) When checked, the fog's Y Scale is set to the X Scale at render time, for uniform scaling.
Detail Controls the detail of the fog. Lower values are smoother, while higher values are more grainy.
Offset Moves the fog, as wind would. In Streaks mode, x rotates the fog around the light, while y moves it toward/away.
Z-Offset Moves the fog through the spotlight along the z-axis (toward or away from the camera).
Shadows
Shadows (Enable) Enables volume shadows
Obscuration Layer The shadow casting map. This layer determines the location and strength of shadow casting objects. The brighter the pixels in the map, the stronger a shadow is casted from them. Black pixels cast no shadow, while white pixels cast a very dense shadow.
Source The method to obtain source values from the Obscuration Layer. Choose from Alpha-Weighted Luminance, Luminance, or Alpha.
Strength Controls how quickly shadows fall off of objects in the Obscuration Layer.
Quality Controls the overall quality of the shadows. 100% is pixel-perfect, but usually unnecessary. 50% or lower will yield very nice results with much less render time.

Transfer Mode The method to composite the effect onto the layer. When set to None, the effect is composited on black.
Opacity Transfer opacity of the effect.