Stereoscopic Vision, Stereoscope, Selection of Stereo Pair and Its Orientation

Stereoscope is to deflect normally converging lines of sight, so that each eye views a different image. For deriving maximum benefit from photographs they are normally studied stereoscopically. Instruments in use today for three dimensional studies of aerial photographs. If instead of looking at the original scene, we observe photos of that scene taken from two different viewpoints, we can under suitable conditions, obtain a three dimensional impression from the two dimensional photos. This impression may be very similar to the impression given by the original scene, but in practice this is rarely so. A pair of photograph taken from two cameras station but covering some common area constitutes and stereoscopic pair which when viewed in a certain manner gives an impression as if a three dimensional model of the common area is being seen.