Nine by nine-inch contact prints are typically provided as stereo pairs. "Old Delft Scanning Stereoscopes" are provided in our research room for viewing of these stereo pairs.
Once the photographs are aligned, these stereoscopes allow 3D viewing of the contact prints in either 1.5 or 4.5 times magnifications. The field of view can be moved in either the X or Y direction to scan the photographs without shifting the stereoscope or prints.
Stereo viewing may also be accomplished without the aid of any specialized optical viewing equipment.
As you gaze at the two photos, cross your eyes very slightly until you see three images. As the left and right images converge into the center image, the three-dimensional effect should become apparent.