the defining range problem is easy- when you click down, that is your zero point, when you roll it up as Fwy as you can, it's equal to spreading your fingers apart as far as you can, and vice versa. Most pinch to zoom apps, i.e. Image galleries, won't zoom in to the max with one pinch; you typically have to use around 3 or 4... Same with the wheel, click down, roll up.. Click down, roll up... Click down, roll up. You could do it at the same speed as pinching, try it on your mouse.