Not all 3D programs have direct correlations between their lighting system and "real world" values. Frankly, it's just not important since 3D programs are intended to create "illusions of reality" rather than simulations of reality. I do know that Lightwave will let you choose color for a light based upon real world light "temperatures" such as Kelvin (among other lighting values) but that's not the same thing you are looking for. Actually, a real world accurate lighting system would be more of a limitation than a boon, since almost every well lit 3D scene requires lighting that would not be possible in the real world, such as certain lights that cast on only certain objects, or that cast no shadow at all. Another common example is the individual selection of shadow casting per object. This would also be tricky with virtual sunlight cast within programs such as Vue, because there would have to be some relative scale coupled with exact placements of light sources to emulate the vast distance between the earth and sun, and that sort of thing is just impracticle for the 3D artist. Best of luck!