Glen Faught takes a look at using IES lights with Cinema 4D to create a more realistic look to scenes, providing accurate falloff, direction and spread to lights that would be difficult to achieve in any other way.
This tutorial covers how to get realistic light falloff and shape with IES lights in Cinema 4D
Here Glen shows how to use the IES lighting profiles and set up the lights in Cinema 4D, and goes beyond using IES lights in Cinema by showing how you can create your own custom light shapes by using a material. Check out the tutorial for Using IES Lights in Cinema 4D for Realistic Lighting and Falloffs here.
IES Files from the Illuminating Engineering Society of North America (IES) provides the standards for lighting engineers, creating a format For the transfer of Luminaire Component Data which most rendering engines can read and use, and Glen also posts some resources for getting some IES lighting profiles to play with.