What is Chiaroscuro?

Here is my personal understanding of how to apply the idea of chiaroscuro in painting.

It is often the case that the value range of a scene is greater than the range of value of your paint. This is particularly clear when painting a candle or a light bulb, but also often occurs in ordinary still life set ups and portraiture. Specular highlights are often much brighter in value than pure white paint. In a grey overcast scene it may be possible to absolutely match all the observed values (think Corot or Messonier), but in a bright scene the range of value is simply too great to mix absolutely in paint. In order to render a bright scene a concession must be made. The value structure must be compressed in some way to allow for the information to be rendered. If you were to try to match things absolutely you would be left with a large blown out area of white, and an area in complete black, resulting in a loss of information, (imagine a blown out photograph).

One such structure for the compression of value in a scene is to reduce the amount contrast everywhere indiscriminately. This will maximize the linear information present but the final painting will read rather dull. Imagine a painting by Jan Van Eyck for example. I will refer to this as a proportionate system.

Another structure for arranging value in paint is to measure things in degrees of contrast rather than absolutely. The quality of the highlight in a scene is often desired to be described by the artist. In this case, the highlight is designated as pure white and then the value of the other parts is determined by the distance in value it is away from the highlight (ie the degree of contrast). If the area adjacent to a highlight is five steps darker than the highlight, then it is rendered five steps darker (eg in nature if a highlight is 15 and then 12, in the painting it may be 10 and then 7). While the absolute value isn’t captured, the distance between values is truthfully and accurately preserved. This is the essence of chiaroscuro. Paintings rendered this way seem luminous and life like, but there is a major concession. You may have noticed that there is not enough room in this system to render the degree of contrast of the darkest values. Caravaggio was okay with this concession and simply made large dark areas of his painting completely black, resulting in a severe loss of information in the shadows. The loss of information has become a major convention in painting and has come to be appreciated as a beautiful aesthetic choice in a composition. However, this is not the full story. Chiaroscuro in practice is used in a slightly more subtle way by most artists in history, where the value of the darkest darks is not brought to absolute black, but rather rendered in an extremely compressed scale. While cameras often indiscriminately render large areas as completely black, artists often preserve faint information of form in the shadows (see the information in the shadows of Tintoretto, Caravaggio, and Ribera). This is achieved by rendering the degree of contrast exactly for the majority of the scene, but rendering the darkest area in a proportionate system. (eg, imagine a scene with range 15-0, with a palette of 10-0. Paint the scene in degrees of contrast for values S15-S6 mapped to P10-P1. Paint the the scene in a proportionate system for values S6-S0 mapped to P1-P0)

Fine art is an aesthetic pursuit. The loss of information in one area may be justified by the preservation of information in another. The quality of light in a painting has the power to captivate the viewer and convince them like magic that what they are seeing is real. The suspension of disbelief allows us to react emotionally and causes new feelings to be experienced.