A Treatise on Painting/Chapter 193
Chap. CXCIII.—How to distribute the Light on Figures.
The lights are to be distributed according to the natural situation you mean your figures should occupy. If you suppose them in sunshine, the shades must be dark, the lights broad and extended, and the shadows of all the surrounding objects distinctly marked upon the ground. If seen in a gloomy day, there will be very little difference between the lights and shades, and no shadows at the feet. If the figures be represented within doors, the lights and shadows will again be distinctly divided, and produce shadows on the ground. But if you suppose a paper blind at the window, and the walls painted white, the effect will be the same as in a gloomy day, when the lights and shadows have little difference. If the figures are enlightened by the fire, the lights must be red and powerful, the shadows dark, and the shadows upon the ground and upon the walls must be precise; observing that they spread wider as they go off from the body. If the figures be enlightened, partly by the sky and partly by the fire, that side which receives the light from the sky will be the brightest, and on the other side it will be reddish, somewhat of the colour of the fire. Above all, contrive, that your figures receive a broad light, and that from above; particularly in portraits, because the people we see in the street receive all the light from above; and it is curious to observe, that there is not a face ever so well known amongst your acquaintance, but would be recognised with difficulty, if it were enlightened from beneath.