Twin-lens camera (c. 1850) and Stereoscope Viewer.
Stereograph cards, along with cycloramas, were a popular form of entertainment before the arrival of the cinema. Much of the battlefield photography in the days following the fighting at Gettysburg was created by artists using their two-lens stereo cameras, as by that date the stereoscope viewer had become a popular parlor entertainment, accessible to most middle-class households. The stereocard below (Recruits going to the front), taken from a section of the Gettysburg Cyclorama, exhibits no 3D effect due to its two-dimensional source material. The other stereocards on this page, however, will demonstrate a stereo 3D effect when viewed in a stereoscope.
