Around 350 BC, Aristotle described the appearance of the picture on a white wall of a darkened room, provided there was a small opening for light on the opposite wall. In 1500, Leonardo da Vinci designed a portable box – camera obscura (darkroom). It was perfected in the 16th century by the enlargement of the light aperture and by inserting a lens, which retained the sharpness of the picture on a smoked glass opposite the hole. When Nicéphore Niépce in 1816 changed the glass with photosensitive material, the first camera for taking pictures was created, and it operated on the principle which is used by modern cameras as well. After he projected light on a metal plate coated with a layer of asphalt and after he developed the image in petroleum, Niépce in 1826 made the first successful photograph. The procedure was perfected by L. J. Daguerre, who used a metal plate coated with silver iodide, which was developed with mercury vapors (daguerreotype, patented in 1839). W. F. H. Talbot patented in 1841 a process called calotype, which was later renamed talbotype. Essentially unchanged, the procedure is still used (black and white negative-positive process).