Bacon devoted ten whole years to the study of optics and some of his best work was done in that field. The principal influence on Bacon in this subject was the work of Alhazen, the Arab. The concentration of rays and the principal focus, knowledge necessary for fine camera work, as well as good picture projection, were familiar to Bacon. This was an advance over Euclid, Ptolemy and Alhazen. Bacon recognized that light had a measurable speed. Up to that time most men thought that the speed of light was infinite. (Measurements were not made until the 19th century.) Bacon also studied the optical illusions pertaining to motion and rest, fundamental for the motion picture. He belonged to the school of vision study that believed we see by something shot out from the objects viewed. This is directly opposed to the idea of Lucretius and others who held that something was shot out of the eye to make sight possible. There is no evidence that Bacon actually invented a telescope but he certainly was aware of the principle. He planned a combination of lenses which would bring far things near. Roger Bacon has often been called the inventor of the _camera obscura_, or “dark room,” which is the heart of the system for taking and exhibiting pictures. (Illustration facing page 40.) However, the original of the modern box pin-hole camera in its simplest form is only a dark room with a very small hole in one wall, and was never actually invented. The phenomenon of an image of what was on the outside appearing upside down in a dark room was surely a natural discovery first observed in the remote past. The “dark room” can easily be considered as a giant box camera with the spectator inside the box. An inverted image of the scene outside appears on the wall or floor with the light coming through a small circular opening, as in a “pin-hole” camera. Record of the first use of the “dark room” for entertainment or science has been lost in the dim past. As late as 1727 the French _Dictionnaire Universel_ suggested, in desperation, that Solomon himself must have invented the room camera. Until the 13th century, the images in the room camera were faint and upside down because no lens system was used. In ancient days and through the Middle Ages the camera was a wonderful and terrifying thing. The theatre always was some small darkened room. With a brilliant sun and the necessary small hole and a white wall or floor, the outside scene would be projected. Spectators and students certainly were thrilled and awed. The Romans learned about the camera from the Greeks, who probably had obtained the knowledge from the East where, with brilliant sun in which the best results could be obtained, it is likely the effects were first noticed. Such learned Arabs as Alhazen are believed to have had a knowledge of the use of the room camera, but Alhazen did not leave any good description of it in his writings.