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
In 1854 the London Stereoscopic Company was formed.
Their chief photographer was William England, whose lively street scenes of