CAMERA. If you darken a room on a bright day and admit no light except through a very small hole in the window shutter, an inverted picture of the objects in front of the hole will be formed on the back wall of the room, or on a white screen placed nearer the window. This is the simplest form of the camera obscura, which means in Italian " dark cham ber"; it was used several centuries ago for observing eclipses. A smaller camera obscura may be made by constructing a small box, with a pin-hole in one side.
If a lens be put in the aperture, a much clearer and sharper image will be formed. If this image is allowed to fall on a plate or film covered with chem icals sensitive to the action of light, and the plate or film is properly developed and " fixed" by other chemicals, a permanent picture is obtained, and the camera obscura becomes a photographic camera (see Photography). The image is more or less dis tinct according to its distance from the lens, and so it is necessary in cameras for fine work to move the lens nearer to or farther from the back wall of the camera. This is done by making the sides of folding leather, and such cameras are called bellows cameras.
If a mirror is put at an angle of 45 degrees inside a camera obscura, an image of the objects before the lens will be formed, right side up, on a piece of ground glass put above the mirror. The viewfinder, with which many photographic cameras are provided, is just a very thin camera obscura of this sort. The periscope, so important in submarine and trench warfare, is a camera obscura arranged to reflect downwards (see Lens; Periscope).
Scientific name of Arabian camel, Camelus arabicus; of the Bactrian camel, Camelus bactrianus.
The llamas, alpacas, and vicunas of South America belong to the same family as the camels, but are smaller in size and differ greatly from them in structure and habits.