It works almost as well as the viewing filter, which few of us carry in our camera bags. In my book, Lighting Techniques for Photographers, I note that contrast can be a very ambiguous term, and I address the technical aspects at great length. But contrast is also analogous to visual impact. That appeal can't be codified. However, we all know what it is when attracted by its presence.
Skilled photographers seek contrast.
But good results usually elude the less skilled because they expect to record everything exactly as they see it. The first version had an astonishingly great range of tones. One of my test examples easily captured every nuance of tone in a contrasty, sun-dappled woodland scene. With the old Kodachrome film, proper exposure for sunny areas had rendered even modest shading almost totally black. The Professional Division had to immediately address these angry attacks.