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.

"the idea of humanism is mostly adeptly reflected in renaissance art by a focus on the body itself, especially with sculpture, where many detailed portraits of the human body (such as the david) were created."