Magic lantern - Three dimensions.

	Viewing stereo photographs was a popular home entertainment in the nineteenth century. It may be compared to the function of the television in our days. The stereoscope was invented in 1838 by Sir Charles Wheatstone, the famous English scientist. He maintained that we perceive depth because each eye sees different images, which are united by the mechanism of the brains. The instruments he made to prove his theory were bulky, because the paired pictures were viewed by means of mirrors. The first improvement was made in 1849 by Sir David Brewster, who not only did away with mirrors, but magnified the pictures with lenses. It was Oliver Wendell Holmes who brought back this box-type stereoscope to a skeleton model that quickly became standard. Because of the relationship with the magic lantern almost every collector of magic lanterns has some stereoscopes in his collection.
Also the rotating of an object can create an illusion of depth. (Cinematograph. Manufacturer Gebrüder Bing, Nuremberg, c. 1913.)

A Holmes stereoscope (c. 1861). A hooded eyepiece fitted with two prismatic half-lenses, slotted support for the cards and a handle to support the whole. Because it was cheap, convenient and efficient, this instrument quickly found its way to almost every household. Other viewers were sometimes as large as a piece of furniture and could store and show fifty or more stereograms.	A lot of photographic companies produced stereo photocards (stereograms) and stereoscopes. Photographers were sent across the world to record famous sights and events in stereo. "See the world from your parlour!", is just one of the many advertising slogans from that time. Of course also all kinds of other subjects were represented on the sets of cards, like stories, nature, and of course.... erotic scenes.
This 3D photocard is made by Universal View Co., William H. Rau, Publisher. The title is "Papa, I like Pictures." A little girl holds a glass Magic Lantern Slide up to the light to view it. There are piles of the slides on her lap and by her side.
Anaglyph
Other techniques for displaying 3D-images use a single image, which contains all the information to reconstruct the full three-dimensional picture. The most common of these is the Anaglyph, which requires the viewer to wear glasses with red and green or cyan lenses. From the left image the blue and green colours are removed to leave a purely red picture while the right image has the red colour removed. The two images are superimposed into one picture with the characterizing red and cyan or green fringes around objects. The red and cyan lenses in the glasses let the eyes separate the two superimposed images into their individual components which the brain then combines to a 3D-image.

Depending on the way of mounting the depicted object is placed behind, in, or in front of a ghost window. The magic lantern in the anaglyph above seems to stick out of the window, into the living room. The lantern on the stereocard below is placed behind the window.

Stereogram Side-by-side 3D photos	There are several ways to view 3D side-by-side photos. The printed photos can be viewed in a parlour-viewer like the Holmes viewer. (Many are still around today.) After some practice most people succeed to do it without a viewer, just by staring beyond the two pictures, seeing a centre 3D image and a left and right peripheral image beside them.

	Download a printable version by clicking the card. 1.5 MB, c. 9 x 18 cm.
This auto-stereogram comes from the site for Magic Eye Inc., www.magiceye.com. The hidden image has something to do with 3D.		Auto-stereogram Hidden images
		Auto-stereograms are 3D images hidden within another picture. The way to discover and view the 3D images is simply to stare at the picture until the image appears. Don't focus at the surface of the picture but try to stare through it, like looking in the distance. Once you begin to see the hidden image, keep looking at it and it will become sharper and more clear. Though the official term for this optical illusion is auto-stereogram, we mostly simply speak of stereogram. The advantage of these stereograms is that they can be viewed without any visual aid.