Hi All
first, thanks to Nicholas for going to all this effort and sharing it with us.
I went to a seminar on rendering in Archicad, run by a very talented artist Dwight Aitken, and the basis of his whole argument was "think like a photographer". Have a look at the photo below;I assure you the walls and ceiling in my house are not Yellow/oragne. They are a pale beige.
Dwight's theory is that the human eye takes "snapshots" of a scene, and the mind blends them all into a memory of the space. So you look into a dark corner, and your eye adjusts to the correct exposure, you turn to the sun, and a second or too later, your eye has adjusted again. For your render to look 'right' you have to trick the renderer by faking the dark areas etc.
In Nicholas's excample, a professional photographer will add extra light to the scene to get the exposure correct in all the areas of the room. These lights are called the 'fill light', and the 'key light'.
Dwight posts a lot here http://archicad-talk.graphisoft.com/viewforum.php?f=3&sid=51852861849d04a35e6732ec14ab5366 and although it's not a VW forum, you may learn something.
Mat