make 3D object lighter or darker

I think it would be great is it was possible to måle a 3d object on a layer lighter ør darker. Because if a draw a character on one bitmap layer and import the background set as an .obj and place it as a lager behind it would be nice to be able to måle the 3d object lighter so it is easier to see the character.
=Mads

I really would be a great help if I easyly could lighten a 3D object (My Set). So I in a fast way could separate My characters draw on bitmap layers from the location which is a 3D object

Kind Regards Mads

I was just thinking why not also make this possible for 2D layers.
If we look at Toby Sheltons examples
http://tobyshelton.blogspot.dk/

We can see that he turns up and down the brightness of the layers to separate the different elements, so maybe it should be possible to add a FX to a layer that you can adjust. A blur would also be nice.
Just some thoughts