Examination of paintings often involves infrared reflectography. The researcher uses invisible, warm infrared light to look beneath the surface and detect features such as an underdrawing, a preliminary sketch made by the artist on the canvas before painting. Some of the infrared light penetrates the top paint layers and is reflected or absorbed in varying degrees by the carbon in the underdrawing. An image captured by an infrared camera, called an infrared reflectogram, shows this drawing in shades of grey. Infrared reflectography can also provide information about the pigments used and about later restorations.