Stereo photography is the practice of capturing and viewing three dimensional images. There are many, many ways to create and present stereo imagery. This site illustrates film and digital camera techniques to produce stereo image pairs using commonly available equipment. A key emphasis of this site is explaining the concept of the Stereo Window - the point in space that corresponds to the image frame of a stereo view. This concept applies to the image capture process and the processes of presenting the image pair to the eyes.
Stereo photography is not for the timid. It's a LOT more fuss than regular 2D photography and, done incorrectly, it can hurt your eyes and give you a headache. Done well, however, stereo images reveal aspects of space 2D just can't convey. One of the easiest ways to achieve excellent results is to use stereo equipment from the '50s (like what's shown below).
This generation of gear is widely available on Ebay and other sites for a few hundred dollars. As of 2007, there are still no reasonably-priced digital stereo cameras. There is another way, however, that will produce excellent results using any camera you already have and about $20 worth of supplies and film. The section on Make Your Own 3D provides step-by-step instruction of the entire process.
If you wonder how all this stuff works, the section on Principles of Stereography provides an introduction to the theories. Stereo photography has a few rules that generally should be followed (like shooting with a small aperture to increase depth-of-field). Of course, some of the best images break the rules, but victimizing people with eye strain is not art.
Hypo- (less than) and Hyper- (greater than) Stereo create images from inter-lens distances less than and greater than normal human interpupillary distance (about 65mm or 2.5 inches). Hypo-stereo is great for extreme closeups and hyper-stereo is great with aerial photography.
Stereo Images: Gimmick or Art?
We humans are fortunate to perceive the world with binocular vision. The overlapping field of view provided by the eyes allows a sense of how far away objects are from oneself, and oneself from everything else.
Many factors contribute to our sense of depth perception, but one is particularly important: As you survey the world around you, your eyes present to your brain not a simple double image, but two views from horizontally offset points of view. These two planar images projected onto the retinae are fused in the brain into one image. The disparity - the distance between corresponding points in each image - provides the cue your mind needs to place you and everything else in three dimensional space.
Although many other techniques exist, the classic means to capture a stereo image is with film. Using a single camera with a normal focal length lens (to mimic human visual perspective), the stereographer can take two images approximately 2.5 inches apart (the average human interpupilary distance) and, with careful presentation of the images to the eyes (a stereoscope or viewing apperatus), recreate the same spatial scene the viewer would see as if she were standing at the original location.
Inventors have created many ingenious devices to capture and present 3D media. Among the most popular is the Victorian Age stereogram print and stereoscope viewer. The stereo photography fad of the 1940s and '50s produced a wide variety of slide film cameras, illuminated hand-held viewers, and projectors. This equipment is not only widely available on the used market, but is relatively inexpensive and offers a refreshingly mechanical interface.
With 3D modeling and image editing software now affordable on personal computers, completely constructed worlds offer an endless playground for virtual stereo cameras. Take a stereo pair of the love of your life with your film camera, scan the images to PhotoCD, whip up a moonscape in Bryce2, collage the scenes in Photoshop, output to film, and your babe's outta this world in 3D.
The ideal of capturing a stereo image faithful to reality (as humans perceive it, that is) involves many considerations and compromises to successfully create the illusion of depth. The photographer draws upon a simultaneous awareness of many technical and aesthetic principles to find the right balance of compromises to capture the image as intended.
Stereo photography (and computer-generated stereo imagery) adds a layer of complexity and many restrictions to the art. A reasonable question to ask is, "and for what?" Does the addition of depth perception return enough reward for the effort? Technically incorrect and aesthetically uninspired images certainly not.
But made with skill and passion, a stereo slide glows like a pair of backlit jewels, offering a private peek into not only a moment in time, but an entire space filled with color, shapes, and depth. Once you've done it in stereo, everything else seems, well…, flat.