by David Gibson
It is fairly simple to take reasonable 3-D shots underground using simple equipment, and a 3-D picture can liven up even the most boring scene. For full details of how to take such photos I would refer the reader to a recent article in 'Descent' (Leonard, David. Descent 43 pp 28-3D) In this article I am only intending to demonstrate an alternative method of viewing the photos - the 'mirror' method.
There are three ways of viewing a Stereo Pair. It can be viewed in a stereoscope or a binocular viewer, it can (if a transparency) be projected in a stereo slide projector or it can be free-viewed. The last method involves relaxing the eyes so that the two images blur together, and then willing them into focus. Once the technique has been mastered it is quite easy to look at 3-D prints this way. It can be difficult to begin with, and bright light helps.
An alternative method, which I have called the 'mirror' method involves printing one half of the pair back to front. This means, of course, that it cannot be viewed in a 3-D viewer - a mirror is needed. The stereo image is not quite as good as with a conventional pair but is easier for 'beginners' to see. (Ideal for breaking the ice at parties??). Place the eyes about 25cm from the photograph and hold a pocket mirror on the right side of the nose. With a bit of juggling, the right hand image as seen in the mirror can be made to coincide with the left hand image as seen direct. The image should then 'snap' into stereo.