Stereophotography (also known as 3D
photography), is a technique for taking
pictures that can afterwards be viewed in a manner that creates a "
stereo" image - an image that appears to have 3
dimensions.
In 1833, Charles Wheatstone made the first images that caused "stereopsis", or the perception of depth. It is interesting to note that such images can be drawn without any special instruments or equipment, and were thus possible long before. He exhibited these drawings with a mirror stereoscope. In 1841, he put this knowledge to use by creating a camera that could take photographs that properly exhibited this effect.
Most commonly, a stereo camera is used to take stereo pictures, as it will expose film from the two slightly different angles at the same time, creating a pair of images that will almost always create the desired effect.
A conventional camera can be used to copy this effect, provided the proper method of viewing, and precision is used when taking the pictures. Essentially, to do so, take a picture of a subject, then move the camera about 7 cm to the side, and photograph the same subject again. This will, in theory, give pictures that can be viewed as a stereogram.
Photographs taken in this manner require a special viewer, a stereoscope. This device causes each eye to view a slightly different image, and the differences in viewing angle are identical to that normally experienced, and thus the picture is seen as having three dimensions.
There was a short time where stereophotography received a lot of attention. Around the end of the 19th century and the early 20th century, there was quite a bit of interest and popularity for stereophotography. It was often used in little entertainment machines that would show images in stereo, and there was even a special mirror device made by Theodore Brown that allowed normal cameras to take stereo photographs.
But today, stereophotography is not often used or viewed by the average person. But it does get a bit of use in the sciences, such as remote survey and medical imaging, as quite a bit more information can be gleaned from a stereogram than from a regular simple photograph, as information on depth is nearly non-existent in such pictures.
Sources:
Stereoscopy: Where Did It Come From? Where Will It Lead?, http://userwww.sfsu.edu/~hl/stereo.html
Stereophotography, http://www.homestead.com/stereophotography/
Blink-O-Scopes: Binocular Cinematography and 3-D Magic, http://www.3dgear.com/scsc/December%20Issue/page3.html