"To be honest, though, I'm just using a solid color texture for most of my IBL, making them hardly Image based lights." I use exactly the same technique, danamongden. I use a diffuse IBL with a very dim intensity for adding "fill" to the overall lighting. Usually, I don't see a need for more than 3 or 4 additional spotlights in the scene after that, and at least one of those will be "specular only". For most outdoor scenes, you shouldn't require more than 3 lights, one of which would be an IBL. You simply can not get the same kind of "fill" with spotlights (regardless of how many you put in the scene) like you can with IBL, and unless I'm trying to match the render to a photo background, I see no need to add an image to the diffuse IBL light itself. Mind you, if you were trying specifically to composite a render into a photo or video background, then that's a different story, and requires some different techniques. ;-)

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Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

System: Pentium QuadCore i7, under Win 8, GeForce GTX 780 / 2GB GPU.