A Brief History and Methodology of Stereoscopic Photography

Stereoscopic photography was invented practically at the same time with conventional photography in 1839. The stereoscope was invented by Sir Charles Wheatstone in England, who also coined its name and introduced it in 1838. It used mirrors to reflect the two pictures to the eyes. Initially it was used to look at carefully constructed drawings and soon after photography was invented the first stereoscopic photographs were also created. The Scotsman Sir David Brewster introduced the first lens stereoscope in 1849 and since then many and varied stereoscopes have been constructed and used. The most famous of these stereoscopes was perfected by the American, Oliver Wendell Holmes around 1859. The latter can be still found in antique shops around the world.

What is Stereoscopic Photography?

Stereoscopic photography is achieved by photographing an image from two slightly different viewpoints at the same time, creating two pictures that look almost identical. When viewing the paired images, the left picture is presented to the left eye and the right picture to the right eye. The brain reconstructs the pictures into a combined single image, which is perceived as a real three-dimensional image. This image has all the cues of a flat photograph, plus the depth that flat photographs do not have. Due to the depth of the image, observers of the image feel as if they are at the actual scene where the photograph was taken.

Shooting Stereo Photographs

Stereoscopic cameras have two lenses that take two pictures at once. The photographer can use standard print or slide film for these pictures. It is possible to use a conventional single lens camera to take very successful stereoscopic pictures as long as the subject doesn’t move. The photographer achieves this by taking one picture and shifting the camera slightly to one side to take another picture, resulting in a stereoscopic pair.

How Are Stereo Images Viewed?  

Since a stereoscopic image is composed of two images, left and right, we must have a method of presenting only one image to one eye, and the other to the other eye. There are many methods that are used to achieve this. Stereoscopes enable us to view stereo prints or slides. Stereoscopes present one view to one eye and the other view the other eye. It is even possible for people to train their eyes to see a stereoscopic image without the aid of any device. One can also project a pair of transparencies on a screen with special projectors and view these with polarizing glasses. The glasses allow each eye to see only one image, left image with the left eye and right with the right eye. Another method which is used in making lenticular photographs employs many narrow vertical lenses molded on a single sheet of plastic, placed on top of many vertical narrow left and right images. Those lenses restrict the angle of view in such a way that each eye sees only the image intended for that eye and from that specific angle. The number of lens/image combination is very large, ranging from 30 to 200 per inch. Yet another system to isolate the two images uses color filter glasses. One image is red, the other blue-green, so that when looking through glasses that have one red and one blue-green filter, only one image is presented to each eye.

What is New in 3D Photography?

Electronic shutter glasses can be used to see stereoscopic images. With such glasses, two slightly different images are presented separately to each eye for a very brief period of time, but because of the persistence of vision, we are fooled to believe that we are looking at a real image from two slightly different angles. These images can be created artificially on a computer, photographed using 3D still cameras, or using 3D motion picture cameras. The electronic goggles present one image to one eye for a fraction of a second, then present the other image briefly to the other eye. This process is repeated many times per second. From these alternating images and because of the principle of persistence of vision, we get the feeling of looking at a real 3D scene in front of us.

Free-Viewing Stereoscopic Images

It is possible to train your eyes to fuse two stereo images without the aid of a stereoscope. Two methods are in use: Parallel Free-Viewing and Cross Eyed Free-Viewing. Some people feel easier using one method and some feel more comfortable with the other. To facilitate all people, we arrange a triplet consisting of the left image, followed by the right image and finally again the left image.

Look at the triplet of images below and initially concentrate on the left and center image. We will try first to train your eyes to fuse these two images in parallel viewing so that your left eye will see only the left picture, and the right eye only the right picture. Let your eyes relax and don’t focus them on the surface of the pictures. Let your eyes gaze into infinity and pretend that you are looking “through” the pictures. Keep staring without focusing your eyes and soon you will see three blurry images. Concentrate on the center image until all of a sudden it will pop clearly in 3D. Now you are using the parallel free viewing method.

Next, we will train your eyes to free-view by crossing them. Concentrate on the center and far right images. Cross your eyes slightly and focus them about half way to the images. Hold the tip of your finger in front of you to help you focus half way. Don’t focus on the images but keep focusing half way by looking at the tip of your finger with the two images behind it and out of focus. Soon you will see three blurred images. Keep staring at the same point until a clear image pops up in 3D.

Congratulations, you are now able to fuse the images by crossing or by parallel viewing the images.

East Side Esplanade, Portland, OR USA

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