Digital Light & Color

Expanding histogram's vertical scale changes how the histogram looks, but the control/mapping curve drawn on the histogram always refers to the unexpanded scale.

For example, 50% gray on a vertical unexpanded scale falls in the middle of it, but when the scale is expanded the same 50% gray is much higher, so the current curve wouldn't map it the way the scale seems to show.

I'm not quite sure how to make it any better though as, even if possible, changing the curve shape to correspond with the expansion of the vertical scale may be just as confusing (maybe not...)?

The y coordinate of the histogram is frequency. The x coord is brightness. Expanding the vertical scale does not affect the horizontal scale which remains linear. Therefore it does not make sense to scale the curve.

I just treated the Y-axis scale as both the frequency for the histogram as well as the output % gray for the X to Y mapping curve. It's all good if I remember that the Y-axis scale when expanded pertains to the histogram only.