The Greek painter Apollodorus (active ca. 408 B.C.) was recognized in antiquity as the inventor of a systematic technique for shading to simulate the appearance of mass and space. He achieved this through the modulation of light and shade, a technique which in Greek was called "skiagraphia."
As with all the famous Greek mural and panel painters, no work by Apollodorus survives, but information about him is preserved in ancient literary sources. His invention of shading is most clearly recorded by Plutarch, De gloria Atheniensium (Moralia, 346A): "Apollodorus, the painter who first invented the fading out (phthora) and building up (apochrosis) of shadow, was an Athenian …." His surname, Skiagraphos (the Shader), is preserved by a scholiast on the Iliad and by Hesychius. Pliny the Elder also seems to be referring to the invention of shading when he remarks that Apollodorus "primus species exprimere instituit" (Naturalis historia, XXXV, 60), a phrase probably to be translated as "he first established a method for representing outward appearance."
The subjects of a few of Apollodorus's paintings are known. Pliny mentions a Praying Priest and an Ajax Burned by Lightning, both in Pergamon. There are also references to a painting of Odysseus wearing a cap, a Herakleidai, and an Alcmena and the Daughters of Herakles Supplicating the Athenians. Little progress has been made in identifying echoes of these pictures in the minor arts or in Romano-Campanian painting. Some traces are preserved, however, on Attic white-ground lecythi dating from the late 5th and early 4th centuries B.C.
It seems likely, based on what little monumental evidence there is to document the beginning of shading in Greek painting, that the first steps taken by Apollodorus in developing this technique involved the use of crosshatching and the thickening of inner contour lines as well as the admixture of light and dark tones. The technique seems at first to have been most commonly used for rendering the folds and mass of drapery, less often for rendering anatomy, and scarcely at all for depicting the spatial setting of figures.
The epigram "You could criticize this more easily than you could imitate it" is said by Plutarch to have been connected with the works of Apollodorus, and if the epigram was composed by the painter himself, it suggests an aggressive, confident personality. Pliny ascribes a Latin version of the same epigram, however, to Zeuxis, a younger contemporary of Apollodorus who also played a role in the development of shading.
Further Reading on Apollodorus
Most of the ancient sources on Apollodorus are collected and translated in J. J. Pollitt, The Art of Greece, 1400-31 B.C.: Sources and Documents (1965). A modern account of Apollodorus is given in Mary Hamilton Swindler, Ancient Painting (1929).