Megalethoscope

thumb|Carlo Ponti's Megalethoscope The megalethoscope is a larger version (mega-) of the alethoscope, (Italian: alethoscopio, from the Greek “true”, “exact” and “vision”) which it largely superseded, and both are instruments for viewing single photographs with a lens to enlarge and to create some illusion of three-dimensionality. They were used to view photographic albumen prints that were coloured, perforated and mounted on a curved frame. Night effects were achieved when viewing pictures in transmitted light from a fitted oil or kerosine lamp and a daytime version of the same scene was seen when lit by the reflected light from two side mirrors. They are sophisticated versions of the peep show, and were designed by Carlo Ponti of Venice before 1862. Lke the similar graphoscope which descends from the eighteenth century zograscope predating photography, these devices were, and are, often confused with the stereoscope which was of a different design and effect. Improvements to the megalethoscope over the alethoscope, mainly the addition of a compound lens, are detailed in ''The Practical Mechanic's Journal'' of 1867.

== Invention == thumb|Ponti's Megalethoscope (Princeton University Library) thumb|Carlo Ponti, Interlaken, Switzerland, night view albumen print shown rear-lit in megalethoscope thumb|Description of Ponti's Megalethoscope Optician, photographer and publisher of views for the tourist and art-connoisseur markets, Carlo Ponti invented the alethoscope in 1860. He presented the device to the Société française de photographie in 1861, then in April, to the Istituto di Scienze, Lettere ed Arti in Venice, earning an honourable mention there in May. He obtained a patent in January 1862 and commenced marketing it and photographs to be viewed using the instrument. His invention was awarded Grand Prix at the International Exhibition in London in 1862. The megalethoscope was produced for him by cabinetmaker Demetrio Puppolin, whose name is inscribed on different models. It was a substantial status symbol, an often elaborate item of furniture that only the well-to-do could afford; some are highly decorated with pearl inlay and marquetry, and they often held collections of photographs in a cabinet beneath.