1. A computer with a monitor viewable program that executes to display a histogram of image data on the monitor, the monitor contemporaneously displaying a screen image viewed on a monitor displaying the histogram, and displays a digital or analog control element that controls both compression and expansion of midtones, wherein activation of the midtone compression/expansion element accordingly alters the displayed image according to effects of programs underlying the control of the element, this histogram display and element being associated on a single logical screen display in which at least one other image data modification effect is present on the screen image as a cursor addressable or keyboard selectable image data modification effect.