The first object of a painter is to make a simple flat surface appear
like a relievo, and some of its parts detached from the ground; he who
excels all others in that part of the art deserves the greatest praise.
This perfection of the art depends on the correct distribution of lights
and shades called _Chiaro-scuro_. If the painter, then, avoids shadows,
he may be said to avoid the glory of the art, and to render his work
despicable to real connoisseurs, for the sake of acquiring the esteem of
vulgar and ignorant admirers of fine colours, who never have any
knowledge of relievo.
_Leonardo._