What can adding contrast do for the overall effect of the artwork?

Upping the contrast produces lighter lights, darker darks, and a wider range of tones in between—making your image look just a little better than what you’d see in real life. On the other hand, reducing contrast can give an image a more flat, even tone. As with saturation, too much contrast is usually not a good thing.

it would usually depend on the genre that they would provide

photography had emerged as an elite art pursued by a few creative individuals for a few wealthy patrons. but now, said bauldelaire, it was succumbing to "the great industrial madness of our times." it was becoming a mass production industry that catered to middle-class tastes, including a taste for gadgetry. the stereoscope, the first 3d imaging system, had turned looking at photographs into parlor entertainment. a "thousand hungry eyes were bending over the peepholes of the stereoscope as though they were the attic-windows of the infinite.