Zograscope

In 1570, John Dee wrote A very fruitfull Preface ... specifying the chiefe Mathematicall Scieces, etc. in which he defined "zographie" as a mathematical art for representing visual images. In 1677, German writer Johann Christoph Kohlhans described the effect of a convex lens in a camera obscura as if the subject appeared "naked before the eye in width, breadth, familiarity and distance". In 1692, William Molyneux wrote in his Dioptrica Nova how "Pieces of Perspective appear Natural and strong through Convex Glasses duly apply'd". Some artists from the 17th-century Dutch Golden Age of painting, like Pieter Janssens Elinga and Samuel Dirksz van Hoogstraten created a type of peep shows with an illusion of depth perception by manipulating the perspective of the view seen inside, usually the interior of a room. From around 1700, many of such "perspective boxes" or "optica" had a bi-convex lens with a large diameter and small dioptre for an exaggerated perspective, giving a stronger illusion of depth. Most pictures showed architectural and topographical subjects with linear perspectives. In 1730, the first zograscopes, then called "optiques", were developed in Paris. Optiques incorporated a mirror, but lacked any simple means of varying the distance of the lens from the image. The term optical diagonal machine dates from as early as 1750. ==Viewing experience==

Zograscopes created an unprecedentedly realistic experience of depicted scenes, so much so that Blake (2003) described it as "virtual reality". ==Explanation==

Magnification of images was well understood by the time the first devices were constructed in the early 18th century. Basically, the image is placed at the focal point of a biconvex or plano-convex lens (a magnifying glass) allowing someone to view the magnified image at varying distances on the other side of the lens. A second way a zograscope could enhance depth perception is by creating binocular stereopsis. Because each eye views the image from a different position, the surface of the picture could have binocular disparity from different magnification for the two eyes or from differences in the rotation of the images received by the eyes, so-called cyclodisparity. or horizontal meridian respectively. As well, coloured parts of the image will be refracted differently for each eye, creating a version of chromostereopsis. Even if the binocular disparity were incorrect for the surface of the image or any coloured parts of it, the stereoscopic information tends to integrate with the other depth information in the image. == See also ==