Expanding Your Value Range -
Having a numbered scale of values makes it easier for artists to discuss specific strategies for using values in paintings. For instance, expanding the value range used to paint an object will make it appear more three-dimensional. The sphere on the left is comprised of three closely related values that have been blended into one another. It seems three-dimensional, but not as three-dimensional as the sphere on the right; this sphere uses the more widely-spaced values of 2, 5, and 8.
Diagram