Top-left lighting is an artistic convention in which illustrations are produced so that the light appears to come from the top left of the picture. The vertical element of the convention stems from the human intuition that sunlight comes from above. Most people prefer lighting from the left when resolving a convex–concave ambiguity, and this preference may be stronger for right-handed individuals.
This convention is reflected in Roman mosaics and in Renaissance, Baroque, and Impressionist art. In cartography, the custom of placing the shadow on the right-hand side of hill profiles was established during the 15th century. Computer interfaces also tend to use top-left lighting (e.g., classic Windows and macOS UI elements), although this trend has gradually shifted more towards light coming straight from the top (e.g., Android key light).
There are notable exceptions to this convention, such as Sandro Botticelli's The Birth of Venus, due to the point of view which may represent geographical perspective and location. Viewing images that do not conform to this convention may produce a form of convex–concave ambiguity.
