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Using a camera lucida. Note that the user sights downward, with the prism reflecting to the eye, in this case, a view of the projector mechanism. The other eye sees the drawing surface.
A commercial camera lucida. The 'home-made' arrangement costs far less, yet results compare very favorably with this unit. The prism can be tilted to a desired angle.
Threshold to Illustration: The Camera Lucida
by Gene Udell
Its Operation
Specialization tends to make paupers of us all. By the time we receive the products of many specialized hands standardization of the instructional product has often intervened between students and ourselves. Teaching becomes, in part, a process of adapting ourselves to instructional material. More effective results naturally occur when instructional materials are made an integral part of our teaching approach— when they are comfortably controlled by us because we have helped to create them. Such is the case with informative drawings.
Competent graphic illustration is considered by many of us to be beyond our effective skills. While currently this may be true, it need not remain so. The instrument known as the camera lucida can become the threshold to illustration for many teachers who now must rely upon commercially prepared illustrations or do without.
The principle of the camera lucida involves literally the tracing of an image (from either two or three-dimensional subjects) which appears to be directly positioned on drawing paper
placed below the camera lucida. The doing is far less complex than the telling how-to-do, but let's see how explicit we can be.
The camera lucida, in one of its several basic forms, consists of a 90-degree prism which is silvered on the base, or hypotenuse surface. In use the prism is caused to be suspended over a drawing surface so that there is free air space between the prism and the table top on which the drawing paper is placed. The drawing paper is positioned directly beneath the suspended prism, while the object to be drawn is placed on a support at the level of the prism.
The user sights downward, looking into the near edge of the prism with one eye and at the drawing paper with the other eye. The image of the object then appears to be "projected" onto the paper and may be traced.
The size of the apparent image is usually not greater than 8 x 10 inches at maximum. Image size is determined mainly by regulating the distance between the prism and the object. The closer the two, the larger the image appears to be; the farther apart, the smaller the image appears.
Where the most finished accuracy is desired.
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Educational Screen and Audiovisual Guide — June, 196(