Camera Lucida

Brass, 8 ½" closed, 20" extended, two additional extension rods. One positive and one negative lens. Leather covered case.

The camera lucida, invented by William Hyde Wollaston in 1807, was a drawing aid and therefore not photographic. It did though give impetus, along with the camera obscura, to the search for a way of permanently recording images direct from nature.

In contrast to the obscura, the lucida does not produce a real image of the subject. The instrument is clamped to the drawing board facing the subject, the user looks down at the top edge of the instrument where part of the eye will see an image reflected by the camera lucida and part will see the drawing paper direct.¹ For the two images to appear co-incident the subject distance should be the same as the distance to the drawing, if this is not the case lenses can be introduced below the instrument to alter the image of the drawing paper, lenses can also be fixed in front of the prism.

The prism is four sided with one internal angle of 90°, another of 135°, the other two angles are equal. The subject is internally reflected by the two obtuse faces.

Simpler instruments using a semi-silvered mirror were commonly provided as microscope accessories and were also known as a camera lucida.

References & Notes:

Cornelius Varley. A Treatise on Optical Drawing Instruments, London, 1845, p. 27. This also shows the Graphic Telescope invented by Varley. Sir David Brewster. A Treatise on Optics, London, 1831. p. 333. Martin Kemp. The Science of Art, chapter IV, gives a very good description of mechanical and optical drawing aids.

[1] Some users may disagree with this statement, give up and draw freehand.

Further Information:

The Science Museum in London previously (when it was a genuine museum) displayed several types of optical drawing instrument. The Museum of the History of Science, Oxford has a camera lucida and Graphic Telescope on display.

Graphic Mirror

Alexander Alexander

Exeter

England

Brass, 8" closed, 13" extended, single additional extension rod. Wooden case.

The Graphic Mirror, introduced by Alexander around 1834, is optically very different to the Wollaston type camera lucida.

In the Wollaston type the eye is placed over the edge of a prism so as to view the reflected image of the subject through the prism and the drawing surface directly.
In the second form the subject is viewed via a semi-reflecting surface, the drawing surface is seen through the semi-reflecting surface.

In very simple instruments produced as toys the semi-reflecting surface might be a sheet of glass. More elaborate devices included semi-silvered mirrors or prisms.

In Alexander's instrument light from the subject passes through a sheet of plain glass and is reflected back by a mirror, the reflected light is reflected up to the eye by the rear surface of the glass and, since the eye sees through the glass, the drawing surface is also seen.

The Graphic Mirror was easier to use than the Wollaston type of lucida and sold in reasonable numbers. A modified form was produced with a hinged tinted glass in front of the regular glass for lithographic use.