"If you were to agree a standard unit of measure, i.e. a meter in your scene corresponds to a "real world" meter, shouldn't preprogrammed light sources be available that give you the results you expect when you place a 60 watt bulb in your lamp at home?" There ARE pre-programmed light sources available in 3D that use the real-world standard of measure, and duplicate the wattage of whatever bulb or light source you want. They're called PHOTOMETRIC LIGHTS. Sorry, but they're not available in Poser. But other apps do have them. 3dsmax comes to mind. Also, at a lower cost, I believe Truespace can also use photometric lights. So this IS something that is out there, and it's not new to 3D. "Wouldn't it be great if you could tell the software to light an outdoor scene as if it were 12 noon on a sunny or overcast day?" Again, this is out there. There's a feature in 3dsmax called a "Daylight System", and it automatically sets up a skylight and direct light rig that corresponds with whatever location on the planet you wish, as well as the time of day you set. There's also HDRI, which allows you to light a scene using "real" light calculations in high dynamic range from special images taken from the real world. This is all possible and available in 3D, I think you just need to research more about what you want. It's been out there for quite a while now.

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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.