Magic lantern

The magic lantern, also known by its Latin name lanterna magica, is an early type of image projector that uses pictures—paintings, prints, or photographs—on transparent plates, usually made of glass, one or more lenses, and a light source. Because a single lens inverts an image projected through it, as in the phenomenon which inverts the image of a camera obscura, slides are inserted upside down in the magic lantern, rendering the projected image correctly oriented. It was mostly developed in the 17th century and commonly used for entertainment purposes. It was increasingly used for education during the 19th century. Since the late 19th century, smaller versions were also mass-produced as toys. The magic lantern was in wide use from the 18th century until the mid-20th century when it was superseded by a compact version that could hold many 35 mm photographic slides: the slide projector.

Technology

Apparatus The magic lantern used a concave mirror behind a light source to direct the light through a small rectangular sheet of glass—a "lantern slide" that bears the image—and onward into a lens at the front of the apparatus. The lens is adjusted to focus the plane of the slide at the distance of the projection screen, which can be simply a white wall, and it forms an enlarged image of the slide on the screen. Some lanterns, including those of Christiaan Huygens and Jan van Musschenbroek, used three lenses for the objective. Biunial lanterns, with two objectives, became common during the 19th century and enabled a smooth and easy change of pictures. Stereopticons added more powerful light sources to optimize the projection of photographic slides.

Slides Originally the pictures were hand painted on glass slides. Initially, figures were rendered with black paint but soon transparent colors were also used. Sometimes the painting was done on oiled paper. Usually black paint was used as a background to block superfluous light, so the figures could be projected without distracting borders or frames. Many slides were finished with a layer of transparent lacquer, but in a later period cover glasses were also used to protect the painted layer. Most handmade slides were mounted in wood frames with a round or square opening for the picture.

After 1820 the manufacturing of hand colored printed slides started, often making use of decalcomania transfers. Many manufactured slides were produced on strips of glass with several pictures on them and rimmed with a strip of glued paper. The first photographic lantern slides, called hyalotypes, were invented by the German-born brothers Ernst Wilhelm (William) and Friedrich (Frederick) Langenheim in 1848 in Philadelphia and patented in 1850.

Light sources Apart from sunlight, the only light sources available at the time of invention in the 17th century were candles and oil lamps, which were very inefficient and produced very dim projected images. The invention of the Argand lamp in the 1790s helped to make the images brighter. The invention of limelight in the 1820s made them even brighter, emitting about 6,000–8,000 lumens. The invention of the intensely bright electric arc lamp in the 1860s eliminated the need for combustible gases or hazardous chemicals, and eventually the incandescent electric lamp further improved safety and convenience, although not brightness.

Precursors

Several types of projection systems existed before the invention of the magic lantern. Giovanni Fontana, Leonardo da Vinci and Cornelis Drebbel described or drew image projectors that had similarities to the magic lantern. In the 17th century, there was an immense interest in optics. The telescope and microscope were invented and apart from being useful to some scientists, such instruments were especially popular as entertaining curiosities to people who could afford them. The magic lantern would prove a natural successor.

Camera obscura The magic lantern can be seen as a further development of camera obscura. This is a natural phenomenon that occurs when an image of a scene at the other side of a screen, a wall, is projected through a small hole in that screen as an inverted image, left to right and upside down, on a surface opposite to the opening. It was known at least since the 5th century BC and experimented with in darkened rooms at least since c. 1000 AD. The use of a lens in the hole has been traced back to c. 1550. The portable camera obscura box with a lens was developed in the 17th century. Dutch inventor Cornelis Drebbel is thought to have sold one to Dutch poet, composer and diplomat Constantijn Huygens in 1622. The oldest known clear description of a box-type camera is in German Jesuit scientist Gaspar Schott's 1657 book Magia universalis naturæ et artis.

Steganographic mirror

The 1645 first edition of German Jesuit scholar Athanasius Kircher's book Ars Magna Lucis et Umbrae included a description of a "Steganographic Mirror" he had invented: a primitive projection system with a focusing lens and text or pictures painted on a concave mirror reflecting sunlight, mostly intended for long-distance communication. Kircher saw limitations in the increase of size and diminished clarity over a long distance and expressed his hope that someone would find a method to improve on this. In Magia universalis, Schott relates how many were using Kircher's technique to exhibit wondrous things to enthusiastic audiences. For instance, the Belgian Jesuit mathematician André Tacquet had shown missionary Martino Martini's complete journey from China to Belgium, when Martini was in Leuven in 1654. Some reports say that Martini lectured throughout Europe with a magic lantern, which he might have imported from China, but there's no evidence that it used anything other than Kircher's technique. However, Tacquet was a correspondent and friend of Christiaan Huygens and may have been a very early adapter of the magic lantern technique that Huygens developed around this period.

Invention

Christiaan Huygens

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