Ok, I think even I get the math on that one (now it's been explained in detail - glad you didn't actually have to get the glove puppets out). See, I said I should know this.

What I think has confused me for so long is specifically with regard to diffuse maps for skin. I almost always find  that caucasian skin maps render unrealistically dark, even in excessively bright lighting.
This is most likely, I realise now, because the creators of the maps are probably depicting somewhat more tanned skin than I am used to seeing around me every day (it's a grim light in the UK so we're paler I guess). But I have tended to both lighten the diffuse maps AND increase the diffuse value - which is most definitely a no-no with IDL.
I do have a dim and distant memory of reading that a diffuse texture should have the appearance of the intended local colours of the object in a perfectly lit environment (whatever that is).

Thanks for going back to basics (I really do suck at math).

 

PoserPro2014(Sr4), Win7 x64, display units set to inches.

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