What are 3D photographs (also called stereo-pairs)?
A "true" 3D photographic image is created by using two images of the same object (in this case mineral and fossil specimens), taken from slightly different viewpoints, and visually combining the images to produce a "Three Dimensional Image" (3D). How the images are taken, combined and viewed will determine the best method for viewing these images.
Stereo-Viewing
The basic concept is to view the left image with, and only with, the left eye and to have the right eye look only at the right image. When properly done a third image will be produced in the center. This third image will be a full 3-D image. This viewing method is know as the "Parallel Viewing" method.
Such a viewing condition is in direct contrast with normal binocular viewing, in which one’s lines of sight involuntarily converge in looking at nearby objects. Because ones lines of sight normally converge involuntarily a greater amount as viewing distance decreases, some method of preventing eye convergence in viewing 3d images is sometimes necessary. Since most people find that it is easier (also more natural) to cross their eyes, stereo images can also be viewed by crossing your eyes. This does require, however, that the photographic images be reversed to insure that the left eye still views the "left eye image" and that the right eye views the "right eye image". We have included two sets of images for each of the pictures, the 1st one uses the "Parallel Viewing" method and the 2nd one uses the "cross your eyes" method. In both cases a white cross can be seen on each of the photos. Use these crosses to an aid in "mentally" combining the two images into a single stereo image.
Method 1
Stare at the center of the stereo-pair in direct line with the white crosses, and pretend that you are staring well beyond the image. Relax and allow the 2 crosses to slowly come together; this might take some practice at first. As the crosses come together you will actually see three images; the one in the middle will be three dimensional. Do not worry initially about the middle image being focused. Relax and your eyes will eventually focus, by themselves, on the image. If you do not succeed right away, don’t panic. This technique does require some patience and practice, however, once you acquire the knack, it will be relatively easy to view the pictures. If you find that you are still having problems after several tries, try this alternative:
Take a piece of cardboard 5" to 6" wide and 12" to 18" in length. The length will vary from one individual to another, so you will probably have to experiment to find out what is comfortable for you (see figure 1). The stereo-pair should now be viewed with forehead and bridge of the nose touching the
cardboard (see figure 2), which separates the images on the left from the image on the right. The
cardboard divider serves to force the left eye to concentrate on the left image and the right eye to
on the right image. With a few seconds concentration on the white crosses, the eyes will
drift apart and assume the straight ahead position of viewing at an infinite distance.. When these
images come together, the correct viewing arrangement has been achieved and the mineral
pictures should "pop" together into a three dimensional view. This 2nd method should work quite
well, however, it still may require some practice and a little patience.
Method 2
The same principle is used for method 2 except that the "left eye" image and the "right eye" image have been reversed. Simply stare at the center of the 2 images in direct line with the 2 white crosses and cross your eyes until the 2 crosses come together as one individual cross. This method works well for most people, however, the one big disadvantage is that when you cross your eyes they tend to become sore after a short time.
The following stereo-pairs are particularly good examples to practice on.
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