I do understand what you mean here John. Indeed it might be difficult to suss out where the ideal separations may be–especially when there are no terminators (attached shadow accents, shadow cores) to define where we often imagine it “should” be. However, any image can be subject to a particular threshold for notan-like separation. You can play around with this threshold in Photoshop. It’s not so much where you “draw the line”, but that you keep it consistent throughout.
