A camera obscura and camera lucida work using different principles, but they both make use of mirrors to let us see the world in a different way. The camera lucida used to be a favorite tool of artists and amateur sketchers, because it lets people trace an image directly onto a page.
The camera lucida was first dreamed up in 1807 by William Hyde Wollaston. We don’t know if he ever made a working prototype, but we do know that by the mid-1800s, camera lucidas were part of many well-off tourists’ traveling kits. Wollaston’s design involved a small box, probably with an adjustable stand, three open sides, and a prism in the middle.
The traveler would position the camera lucida over a piece of paper with one open side looking down at the piece of paper, the other one facing their eyes, and the third pointing at whatever they wanted to capture—usually a beautiful landscape or old building. The sides of the prism would refract the image of the landscape so it would be superimposed on the image of the piece of paper. From there, travelers could trace the scene onto the piece of paper and bring it home to their friends.
Camera lucidas were notoriously difficult to use. Depending on the levels of light, the color of the paper, and the brightness of the landscape, one image could entirely wash out another. It’s easy to see why actual cameras caught on. The camera lucida is still being used, though many today use half-silvered mirrors instead of prisms. Art students use it to trace images, either to make an exact copy of a piece of art or to get a sense of how to use lines, sketch perspective and proportion.