Thanks for the info. I've had problems with color differences between Unreal and Photoshop before; I'll look into the sRGB setting. And thank you for pointing out the VectorToRadialValue function. It helped me optimize my own function, and I think mine might be a bit better than UDK's now. UDK's function is 61/107/49…
Light functions are only available on dynamic lights. So the most important cost will be the fact that you use a light function, but that you use a dynamic light.