Right. If 10% of your light bounces off the object, then you have only 90% left to either be absorbed by the surface, or to continue through the surface by transparency. To use an extreme example, you can't have an object that's 100% transparent and 100% reflective. That would mean that all of the light is passing through and all of the light is also bouncing off. I was never a Ray Dream user, but I played with it years ago and it handled this issue nicely - if I remember correctly, reflection and transparency were handled with a single slider control with two little arrows, one for transparency and one for reflection, Since they couldn't pass each other on the slider, it was impossible to get the percentages to overlap unrealisticallly. If you wanted more transparency you'd have to reduce the reflectivity. It was slick. I'm sure many of you are more familiar with this feature of Ray Dream. Still, in a more-strict physical model I would think that absorption of light should be handled in the same way, but as I recall it wasn't. - Joe