ACADEMIE IMPERIALE - Vue interiere de la Cathedrale de St.Paul a Londres.

So-called optical print, engraved by F.Leizelt. In the eighteenth and nineteenth centuries there were many popular speciality establishments in Paris, Augsburg and London, which produced optical viewing devices and special engravings to be viewed through them. In the 18th century the "optical print" or "vue optique" came into existence, whose exaggerated converging lines were intended to produce the optical illusion of deep recession. The viewing devices for which these perspective prints were produced consisted of a lens and a mirror, this requiring the use of reversed or mirror-image pictures.