I've looked in the book and there's not a whole lot of explanation.
That bar that floats around in the background of the 4 points, what's that supposed to be and why does it swing around wildly when I'm adjusting one or two of the points?
What are the specific definitions of each of the 4 points? I.e., what do they represent exactly?
Does anyone have a solid grasp of this FX? I think it's probably superb, but when I use it, it's a hit or miss thing - I don't really know what I'm doing.

Thanks for your help; you're always there when I need you.