LIGHTS, in Painting, are those parts of a piece which are illuminated, or that lie open to the luminary by which the piece is supposed to be enlightened; and which, for this reason, are painted in bright vivid colours.
In this sense, light is opposed to shadow.
Different lights have very different effects on a picture, and occasion a difference in the management of every part. A great deal therefore depends on the painter's choosing a proper light for his piece to be illuminated by; and a great deal more, in the conduct of the lights and shadows, when the luminary is pitched upon.
The strength and relief of a figure, as well as its gracefulness, depend entirely on the management of the lights, and the joining of those to the shadows.
The light a figure receives is either direct or reflected; to each of which special regard must be had. The doctrine of lights and shadows makes that part of painting called clair-obscur.