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A camera lucida is a drawing aid that allows an artist or illustrator to see an image of an object superimposed upon a sheet of paper, so that the object can be drawn accurately by tracing the outlines. This centuries-old device uses mirrors and an eyepiece to create the superimposed image. Both antique and modern versions are still in use by artists and scientific illustrators.
Dr. William Hyde Wollaston patented the instrument in 1807 as an aid for painters and other artists; however, it is possible that a similar optical device was used in earlier times: something resembling a camera lucida was described by the astronomer and mathematician Johannes Kepler in the 17th Century. The camera lucida as an aid to painting and drawing was preceded by other optical devices such as the camera obscura, a type of pinhole camera; and the Claude glass or black mirror, a dark-tinted mirror which was used to highlight objects to be painted against their backgrounds and simplify scenes. The artist David Hockney has presented a theory that the old masters, including Ingres, Van Eyck and Caravaggio, might have used the camera lucida and other optical aids, citing as evidence the changes in painting style that coincided with developments in the science of optics.
The device consists essentially of a prism, or a set of mirrors, and an eyepiece on an adjustable stand. One side of the prism, or one of the mirrors, is half-silvered, so that half of the light reaching it will be reflected and half will pass through. The camera lucida is adjusted so that the artist is looking down from the eyepiece through the half-silvered mirror toward the paper below. Meanwhile, light from the object to be drawn enters this mirror at a 45 degree angle, is reflected back onto it by a conventional mirror, and a proportion of the light is then reflected into the eyepiece, along with the light from the paper.
In this way, the artist sees both the object to be drawn and the paper, along with her hand and pencil while she is drawing. A broadly similar method is used to create the “Pepper’s ghost” optical illusion, where an image originating in a hidden, darkened room positioned to the side of the viewer appears, reflected in a half-silvered mirror, superimposed upon the view ahead. It is commonly employed in “haunted house” style attractions.
Antique and replica specimens of the camera lucida are available, but modern versions of the device are still employed today. In some circumstances, a detailed manual illustration of an object can be more useful than a photograph, as certain elements can be emphasized to make them more obvious to the viewer. This is particularly the case in fields such as paleontology, paleobotany and neurology, where it is necessary to clearly depict structures that might not be picked up well by a camera. Scientific illustrators will sometimes use a modern camera lucida to capture this detail manually.