Spot Light Controls

Spot Radius

The radius of the circle that emits light. If the spot light is seen as a cone, this is analogue to truncating the cone tip where the cone has a radius equal to Spot Radius. A very small value makes the cone near ideal. Increasing the Spot Radius will soften the lit region edge and the shadows casted by the spot light.

Visible to Camera

Makes the light source visible to the camera (a.k.a primary rays). 

Drop Off

Specifies the rate at which the light intensity decreases from the spot light beam center to the edge.