Zograscope

Rod Bantjes Collection, #RB-01

English(?) late 18^th century

Dimensions: H=59 cm, W=24 cm, D=31.3 cm (with mirror open)

Lens: ⌀=12 cm, ƒ=152 cm

 

Figure RB-01.1 –Zograscope
Photo © Rod Bantjes, 2025.

Figure ZG.1 – Zograscope in Use
Photo © Ana David Mendes.

This is a biconvex-lens viewer for enhancing the 3D-effect of copper-plate engravings known as vues d'optique.

 

It is an example of an “optical machine.” Zograscopes are distinguished from other diagonal-mirror viewers in the Optical Machine Taxonomy by the fact that they have no enclosing box or image-holder and so rely on a surface such as a table to support the image.

 

To appreciate the 3D effect you must look through the lens with both eyes at the image of a print reflected in the mirror (see Figure RB-01.2). You position the print upside-down at the base of the zograscope. Since the mirror reverses the print left-to right, vues d'optique often had titles printed in reverse so that they could be read when seen through the device.

 

This zograscope has a thumbscrew near the top of the column for adjusting the height of the lens-mirror assembly, so that the user can find the position that gives them the best 3D effect. Eighteenth-century writers recommend that distance between the print should and the lens should be approximately the focal length of the lens. That distance would make the direction of the two eyes parallel when looking at the surface of the print, just as they would be when looking at a distant horizon. This is supposed to make depicted landscapes appear to be at a great distance, and the illusion of a great space to open up before the viewer.

The 3D Effect

The zograscope is one of the most common forms of the “optical machine” – any viewer that uses a convex lens or concave mirror to enhance the 3D effect of an image. There are close to a hundred different varieties of optical machines, but the optical principles are the same for all of them, and you can follow this link to learn more about how it works .

 

The focal length of this lens is unusually long (152 cm), close to 3 times the distance to the image. While it does not conform to 18^th-century theory, it still produces a weak spatial effect.