Throughout its history, stereoscopic photography has had numerous ways of producing and presenting images. It all started out in 1833 as Sir Charles Wheatstone came up with using two slightly different images that would be shown as one through a crude stereo viewing device. This device came to be known as the stereoscope.
The techniques used for producing and viewing stereoscopic images would keep on evolving, but it wasn't until 1939 that a man named William Gruber worked together with Harold Graves to turn a flexible 35mm film by Kodak into photo casting reels that would make the devices portable and contain several photographs that would easily change with just a flick of a switch. This device eventually turned out to be one of history's beloved classic toys.
Stereoscopic photography works by showing two similar images with slight differences in the angle they were taken at. These photographs aim to simulate how the eyes would see a certain object since both eyes have slight differences as they are slightly apart from each other. So when producing stereoscopic photographs, two photos are taken with an approximate distance of 2.5 inches from each other. This difference is what produces depth that creates the 3D effect.
There have been different devices used for viewing these photographs, all of which involved peeking through viewfinders for each eye that would isolate their vision and focus it on the photographs. Back then, the photographs would be held by a stick, and binocular-like viewfinders would zoom in on them. Some devices were big enough to contain a stack of photographs, while others were a bit smaller.
The arrival of the View Master
Since many of the older types of devices used photographs printed on paper, they all had to be a bit bigger so they could house the two photographs. However, when Gruber and Graves thought of using tiny films instead of larger printed photos, they were able to make a small device with casting reels that made viewing the images a lot easier. They would call this device the View Master.
Since its creation in the 1940's, this device has continued to be a classic with its trademark red body and fun 3D photograph viewing. To know more about the history of stereo photography and View-Masters, you can visit arts.rpi.edu/~ruiz/stereo_history/text/historystereog.html.
The Casting Reels of the Classic Red View-Master