Contrast Inflection Point

A user adjustable inflection point for the Contrast slider would be a useful feature, making Contrast a semi-parametric control - one that would be more intuitive and easier to control for routine adjustments than curves or levels.  I'm not sure how useful variable Q would be.

Related: a histogram (or curve) option displaying the total applied luminosity adjustments, including the manufacturer or default curve, independent of the actual image data - show the net global luminosity curve.