The Shadows/Highlights tool was one of the major new features to be released with the first version of Photoshop CS.
The tool uses sliders, and so carries the advantage of being quick and easy to use, although with the possible disadvantage of “hiding” some of the information.
In particular, it works differently from the other optimization tools, such as Curves and Levels, with algorithms to control effects across specific tonal ranges. Its primary intent as designed by Adobe is to lighten shadows realistically, in particular for backlit images. However, its algorithms for altering the contrast in the midtones alone are possibly more important for many photographers.
What makes this dialog special is that the lightening ...