| What is "Stereo" or "3D"? |
The word "stereo" originates from the Greek and means "relating to space". Today, when we talk about stereo, we usually refer to stereophonic sound. Originally, the term was associated with stereoscopic pictures, which were either drawn or photographed. In order to avoid confusion with stereophonic sound, one now often talks about 3D pictures and especially 3D-film, where 3D, of course, stands for three-dimensional.
A person lives in a three-dimensional, spatial, environment. Without a feeling for space, we can not move within it. Our perception of space is created almost exclusively by our eyes. There are many ways to orient oneself in space, e.g., by perspective, gradation of color, contrast and movement.
The lenses of the eyes in a healthy human being project two slightly different pictures onto the retinas, which are then transformed, by the brain, into a spatial representation. The actual stereoscopic spatial observation is a result of this perception through both eyes.
A number of otherwise healthy two-eyed people, however, have eye-defects since birth, that make stereoscopic viewing impossible. As babies, they have, in the literal sense of the word, learned to "grasp" the world. They safely orient themselves in their environment by employing one of the other above mentioned methods. Even a person with only one eye learns how to move around safely, using non stereoscopic cues.
The normal picture on paper or film is only one-eyed. It is photographed with only one lens and can, therefore, not convey a true spatial perception. It is only a flat picture. But we do not have to abstain from the known natural effect. By taking two lenses and imitating the eyes, we can create such a space image.
When we examine with or without optical instruments a stereo picture created in such a manner, we form a similar perception of space in our mind.
The two necessary, somewhat different, single views can be generated by different methods. We can produce them like the old stereo artists did, first draw one, then the other single view. We may also take the exposure one after the other with a normal single lens camera. It is evident that the subject must not move during this procedure, otherwise the two pictures would be too different. A better approach is to imitate the head and mount both lenses in a common chassis. Now we have a true stereo camera. Basically it is only the joining of two mono-cameras. It is also possible to take stereo pictures with two coupled cameras. The two lenses can also be combined as interchangeable stereo optics in a single camera.
3D-Photography duplicates the way we view a 3D object or scene by taking a pair of photographs separated by a distance equal to the separation between a typical person's eyes. The two pictures then have a viewpoint similar to the view seen by the left and right eye. These images, if directed to the left and right eyes, are fused by the brain into a single image with the appearance of depth. Perhaps the most well-known example of this is the View-Master™ many of us have played with as children (of all ages).
A quick look in the dictionary will give you a basic idea of the terms "Stereoscopy" and "Stereoscopic Photography":
Stereoscopy
Science and technology dealing with two-dimensional drawings or photographs that when viewed by both eyes appear to exist in three dimensions in space. A popular term for stereoscopy is 3D. Stereoscopic pictures are produced in pairs, the members of a pair showing the same scene or object from slightly different angles that correspond to the angles of vision of the two eyes of a person looking at the object itself. Stereoscopy is possible only because of binocular vision, which requires that the left-eye view and the right-eye view of an object be perceived from different angles. In the brain the separate perceptions of the eyes are combined and interpreted in terms of depth, of different distances to points and objects seen. Stereoscopic pictures are viewed by some means that presents the right-eye image to the right eye and the left-eye image to the left. An experienced observer of stereopairs may be able to achieve the proper focus and convergence without special viewing equipment (e.g., a stereoscope); ordinarily, however, some device is used that allows each eye to see only the appropriate picture of the pair. To produce a three-dimensional effect in motion pictures, various systems have been employed, all involving simultaneous projection on the screen of left- and right-eye images distinguished by, for example, different colour or polarization and the use by the audience of binocular viewing filters to perceive the images properly. In holography the two eyes see two reconstructed images (light-interference patterns) as if viewing the imaged object normally, at slightly different angles.
Stereoscopic Photography
Many of the landscape photographers also took stereographs. These double pictures, taken after 1856 with twin-lens cameras, produce a remarkable effect of three dimensions when viewed through a stereoscope. Stereography, first described in 1832 by the English physicist Charles Wheatstone, is uniquely photographic, since no artist could draw two scenes in exact perspective from viewpoints separated only 2½ inches - the normal distance between human eyes. Wheatstone's mirror stereoscope, however, was not practical for use with photographs, and the invention languished until the Scottish scientist Sir David Brewster designed a simplified viewing instrument, which was exhibited at the 1851 Great Exhibition in the Crystal Palace, London. Queen Victoria was entranced by the stereo daguerreotypes she saw there, and with the introduction of the collodion process, which simplified exposure and printing techniques, three-dimensional photography became a popular craze.In 1854 the London Stereoscopic Company was formed. Their chief photographer was William England, whose lively street scenes of New York City in rainy weather and views of Niagara Falls taken in 1859 were the wonders of the day. The instantaneous street scenes, which showed pedestrians and vehicles stopped in their tracks, were made possible because the small size of the stereo-camera reduced exposure times to less than half a second. To minimize movement street views were usually taken from a first-floor window with the camera focused directly down the street. (Such views later inspired several Impressionists to paint similar street scenes.) Between 1860 and about 1920 a stereo viewer was as ubiquitous in British and American homes (where a simplified and cheap hand viewer was introduced by Oliver Wendell Holmes [the American physician was a great lover of photography]) as the television set is today. Millions of stereographs were circulated in the years before newspaper reproduction of photographs, and their impact was enormous.
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