This is a question to Lee on his Volumetric renders. You get your materials to look phenomenal, waxy, subsurface scattering and in other cases, very solid, like plaster. I have followed your head tutorial (see examples below) Where do you place the range function? Before or after the camera projection. I have tried both and the MAX output seems very sensitive to me....I can not put a value in max above .2-.4 usually to not distort the geometry to unrecognizable. This is far from the 8 value you say to try in the tutorial. I have tried many textures and have a long way of experimenting to find which work best, and how to overcome stepping or blocks in the volume render. I am very thankful for your tutorials and the help you have given, but would love to get more of the contrast and beauty you get into your volumes.
Nice progress! The Range should go directly to the Displacement of the Standard Volume shader. This should give you the control that you need. Yes, the values are quite sensitive. I also added a ramp before the texture to give more falloff between the head and the volume. I would try adding some more directional lighting to the scene. Hope that helps!
A very basic example.
Range is nice everywhere, also let's say you import a map that sits in normal range 0-1 you can easily scale it to vector space -1 to 1 and so forth.