The word “chiaroscuro” translates as “light-dark” in Italian. Generally it means the management of light and dark tones in a picture. As an art term, it has a variety of specific meanings.
Originally it referred to a way of drawing on tone paper using white paint for the lighter areas and ink for the shadows. It also can describe a type of woodcut block printing where separate blocks are used for different degrees of tone.
More often it describes the use of bold contrasts of illuminated areas versus shaded passages within a composition, as with this Caravaggio. The effect conveys not only realism of appearance, but psychological tension.
Note the separation of light and dark tones. Caravaggio doesn’t muddle around very much with transitional halftones or reflected light. To achieve this tonal separation with a posed figure, the model stand needs to be surrounded with dark cloth to suppress fill light.
Sometimes this effect is called “tenebrism,” especially in association with 17th Century followers of Caravaggio in Spain and Italy.
Chiaroscuro is also often associated with candlelit scenes. In this painting by Georges De La Tour, the light source comes from within the picture and the overall effect is dark and dramatic. Note the subsurface scattering in the child’s fingers.
Finally the term is used to refer to the use of controlled tonal modeling to convey dimensionalism in anatomical form. Peter Paul Rubens’ “Elevation of the Cross” is a good example of this sense of chiaroscuro. The image has a bulging, rippling, “formy” appearance.
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